# Product Requirements Document (PRD) - Angular Clarity Boilerplate

## 1. Product Vision

To provide a robust, scalable, and feature-rich boilerplate that serves as a foundational template for building modern, enterprise-grade web applications using Angular and the VMware Clarity Design System. The vision is to accelerate the development lifecycle by offering a pre-configured, best-practice project structure.

## 2. Target Audience

The primary target audience consists of **Angular developers and development teams** who require a standardized, efficient, and consistent starting point for new projects. This includes:

* **Enterprise Development Teams:** Teams that need to maintain a consistent look and feel across multiple applications.
* **Independent Developers:** Individuals looking to quickly bootstrap new projects without spending significant time on initial setup and configuration.

## 3. User Stories (Developer Stories)

### User Story 1: Quick Project Initialization
- **As a developer, I want to clone the repository and run `npm install` and `ng serve` to get a live development server running, so that I can bypass manual setup and start building features immediately.**
- **Acceptance Criteria:**
    - Given I have Node.js and Angular CLI installed,
    - When I clone the repository, install dependencies, and run the start command,
    - Then the application compiles successfully and is accessible in my browser at `localhost:4200`.

### User Story 2: Add a New Feature
- **As a developer, I want to create a new lazy-loaded feature module with its own components and routing, so that I can add new sections to the application in a scalable way.**
- **Acceptance Criteria:**
    - Given the boilerplate is running,
    - When I use the Angular CLI to generate a new module and add it to the main routing configuration,
    - Then I can navigate to the new feature's route, and its components are rendered correctly.

### User Story 3: Utilize Shared Components
- **As a developer, I want to use a component from the `SharedModule` within a new feature module, so that I can reuse common UI elements and maintain consistency.**
- **Acceptance Criteria:**
    - Given I have a new feature module,
    - When I import the `SharedModule` into my feature module,
    - Then I can use the shared components (e.g., a custom card or loader) in my feature's templates without errors.

## 4. Functional Requirements

- **FR-001: Pre-configured Angular Environment:** A ready-to-use Angular CLI project with all necessary dependencies and build configurations.
- **FR-002: Clarity Design System Integration:** Full integration of Clarity UI components and styles, ready for immediate use.
- **FR-003: Scalable Architecture:** A modular structure featuring a `CoreModule` for singleton services and a `SharedModule` for reusable UI components, directives, and pipes.
- **FR-004: Responsive Layout:** A default application shell with a responsive header, navigation sidebar, and main content area.
- **FR-005: Routing:** A pre-configured routing module with examples of lazy-loaded feature modules.
- **FR-006: Theming:** Basic support for Clarity's light and dark themes.

## 5. Non-Functional Requirements

- **NFR-001: Performance:** The initial boilerplate should be lightweight, ensuring fast development server startup times and optimized production builds.
- **NFR-002: Usability (Developer Experience):** The codebase must be clean, well-commented, and logically organized to provide an excellent developer experience.
- **NFR-003: Maintainability:** The modular architecture must facilitate easy updates to dependencies and allow for the addition of new features without introducing breaking changes to the core structure.
- **NFR-004: Scalability:** The architecture is designed to support the growth of large, enterprise-scale applications.
- **NFR-005: Extensibility:** The boilerplate should be easy to customize and extend with additional libraries, modules, and configurations as per project-specific needs.

## 6. Out of Scope

The following features and functionalities are explicitly out of scope for the boilerplate:

-   **Backend Implementation:** This is a frontend-only boilerplate and does not include any backend code or database.
-   **Authentication/Authorization Logic:** While the architecture supports the implementation of security features, no pre-built authentication or authorization logic is included.
-   **State Management:** The boilerplate does not include a state management library (e.g., NgRx, Akita) by default, allowing developers to choose the best solution for their needs.
-   **Business Logic:** No specific business logic or application features are included beyond the basic structural components.
-   **CI/CD Pipelines:** While the project is ready for CI/CD, no pre-configured pipelines are included.

---

## PRD UPDATE - 2025-10-10 04:23:38

# Product Requirements Document (PRD)
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## 1. Executive Summary
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The Messaging App project aims to deliver a robust, real-time communication platform built by extending an existing Angular Clarity boilerplate for the frontend and developing a new, dedicated Python FastAPI backend. The initial MVP will focus on core functionalities including secure user authentication, real-time one-to-one text messaging, and persistent message history. The project emphasizes scalability, security, and a seamless user experience, addressing the need for instant and reliable digital communication as outlined in the `analysis_document.md`.

## 2. Product Vision & Strategy
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**Product Vision:** To be a secure, highly performant, and intuitive real-time messaging application that enables effortless communication between users, built on modern, scalable web technologies.

**Strategic Goals:**
1.  **Achieve Core Messaging MVP:** Successfully launch a stable and functional platform for authenticated users to engage in one-to-one real-time text chats with message persistence.
2.  **Ensure Scalability & Performance:** Design and implement an architecture capable of supporting a growing number of concurrent users and high message volumes with low latency (NFR-PM-001, NFR-PM-002).
3.  **Prioritize Security:** Implement robust authentication, authorization, and data encryption to protect user data and communications (NFR-PM-003).
4.  **Leverage Existing Assets:** Seamlessly integrate with and extend the Angular Clarity boilerplate to provide a consistent and modern UI/UX.
5.  **Enable Future Expansion:** Lay a flexible architectural foundation for easy integration of future features like group chat, media sharing, and notifications.

**Success Metrics (KPIs):** (See Section 11 for detailed KPIs)

## 3. Target Users & Personas
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**Primary Target Users:** Individuals and small teams who require a reliable, instant, and secure digital communication tool. These users value privacy, real-time interaction, and an intuitive user interface. (Referenced: `analysis_document.md` User Requirements)

**Persona: Emily, The Connected Professional**
*   **Demographics:** 32 years old, Marketing Manager, tech-savvy.
*   **Goals:** Stay in touch with colleagues and clients instantly, share quick updates, maintain a professional digital presence.
*   **Pain Points:** Existing tools are often clunky, not real-time enough, or lack a clean interface. Concerned about data privacy and security with public messaging apps.
*   **Needs:** Fast and reliable one-to-one messaging, clear presence indicators, easy access to chat history, secure communication. A clean, intuitive interface that doesn't distract.
*   **User Journey (MVP Focus - Exemplar):**
    1.  **Discover & Register:** Emily hears about the app, visits the website, registers a new account using her work email.
    2.  **Log In:** Logs in securely using her credentials.
    3.  **Find Colleague:** Searches for her colleague, Mark, by his username or email.
    4.  **Initiate Chat:** Clicks on Mark's name to open a new chat window.
    5.  **Send Message:** Types a message and sees it delivered instantly.
    6.  **Receive Reply:** Receives Mark's reply instantly.
    7.  **View History:** Scrolls up to see previous messages in her conversation with Mark.

## 4. Problem Statement
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Users require a digital communication platform that offers **instant, reliable, and secure messaging capabilities**, yet existing solutions often fall short in one or more areas such as user-friendliness, consistency in real-time delivery, or robust data privacy. The challenge is to provide a seamless user experience that fosters efficient interaction while ensuring the underlying architecture is scalable and secure enough to handle the demands of modern real-time communication. (Referenced: `analysis_document.md` Problem Statement)

## 5. Solution Overview
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The Messaging App will be a **real-time, full-stack application** comprising a responsive Angular Clarity frontend and a high-performance Python FastAPI backend, supported by PostgreSQL for persistent data and Redis for real-time operations. The solution will provide:
*   **Secure User Management:** Registration, login (JWT-based), profile management, and user search.
*   **Real-time One-to-One Messaging:** Instant delivery and display of text messages via WebSockets.
*   **Persistent Chat History:** Storage and retrieval of all messages for ongoing conversations.
*   **Intuitive User Interface:** A clean, consistent, and responsive UI leveraging the VMware Clarity Design System.
*   **Scalable Architecture:** A modular, microservices-oriented backend designed for horizontal scaling to handle increasing user load and message volume. (Referenced: `analysis_document.md`, `architecture_document.md`)

## 6. Functional Requirements
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**6.1. User Authentication & Profile Management (MVP)**
*   FR-PM-001: User Registration: Allow new users to create an account with a unique username, email, and password.
*   FR-PM-002: User Login/Logout: Enable registered users to securely log in and out of the application.
*   FR-PM-003: User Profile View/Edit: Allow users to view and update their profile information (e.g., username, optional profile picture).
*   FR-PM-004: User Presence Display: Display the online/offline status of users to their contacts.
*   FR-PM-005: User Search: Enable users to search for other registered users by username or email.

**6.2. One-to-One Real-time Messaging (MVP)**
*   FR-PM-006: Conversation List: Display a list of all active one-to-one conversations for the logged-in user.
*   FR-PM-007: Send Text Message (1:1): Allow a user to compose and send a text message to another specific user in real-time.
*   FR-PM-008: Receive Text Message (1:1): Ensure incoming text messages from another user are displayed in real-time.
*   FR-PM-009: Message History Retrieval (1:1): Automatically load and display historical messages for a one-to-one conversation.

**6.3. Group Chat (Phase 3)**
*   FR-PM-010: Create Group Chat: Allow users to create new group conversations and invite other users.
*   FR-PM-011: Manage Group Members: Enable group administrators to add or remove members from a group chat.
*   FR-PM-012: Send Text Message (Group): Allow users to send text messages within a group conversation.
*   FR-PM-013: Receive Text Message (Group): Ensure incoming text messages within a group are displayed in real-time for all group members.
*   FR-PM-014: Message History Retrieval (Group): Automatically load and display historical messages for a group conversation.

**6.4. Notifications (Phase 3)**
*   FR-PM-015: New Message Notification: Alert users to new messages when they are not actively viewing the conversation.
*   FR-PM-016: User Status Notification: Notify users when a contact comes online or goes offline (optional).

**6.5. Media Sharing (Phase 3)**
*   FR-PM-017: Share Image/File: Allow users to upload and share images or other files within a chat.
*   FR-PM-018: View Shared Media: Display shared images/files appropriately within the chat interface.

## 7. Non-Functional Requirements
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*   **NFR-PM-001: Performance:** Message delivery latency should be consistently below 500ms under normal load. Initial page load for the frontend should be optimized for speed. Backend API response times should be under 200ms. (Referenced: `analysis_document.md` NFR-001, `architecture_document.md` Scalability Considerations).
*   **NFR-PM-002: Scalability:** The system must support at least 1,000 concurrent users for the MVP, with architectural provisions to scale to 10,000+. Backend services must be horizontally scalable. (Referenced: `analysis_document.md` NFR-002, `architecture_document.md` Scalability Considerations).
*   **NFR-PM-003: Security:** Implement JWT-based authentication for all API and WebSocket connections. User passwords must be securely hashed. All communications (HTTP/WebSocket) must be encrypted via TLS/SSL (HTTPS/WSS). Comprehensive input validation to prevent common attacks. (Referenced: `analysis_document.md` NFR-003, NFR-004, NFR-005, NFR-006; `architecture_document.md` Security Architecture).
*   **NFR-PM-004: Reliability:** Messages sent should be reliably delivered and persisted. The system should gracefully handle network interruptions and service failures with appropriate error handling and user feedback. An offline message delivery mechanism (using Redis Streams/Lists) must be in place. (Referenced: `analysis_document.md` NFR-011, NFR-012; `architecture_document.md` Data Architecture Refinement).
*   **NFR-PM-005: Usability:** The user interface, built with Angular Clarity, must be intuitive and responsive across various screen sizes and devices. (Referenced: `analysis_document.md` NFR-007, NFR-009).
*   **NFR-PM-006: Maintainability:** The codebase must be modular, well-documented, and adhere to industry best practices to facilitate easy updates and feature additions. (Referenced: `analysis_document.md` NFR-013, NFR-014).
*   **NFR-PM-007: Real-time:** Core messaging functionalities (sending/receiving messages, presence updates) must operate in real-time with minimal perceived delay. (Core project requirement).

## 8. Epic Stories
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### Epic 1: User Authentication & Profile Management (MVP)
**Epic Description:** Enable users to securely create and manage their accounts, including registration, login, profile updates, and the ability to find other users for communication.
**Business Value:** Provides foundational access control and identity management, essential for any multi-user application. Allows users to personalize their experience and connect with others.
**Acceptance Criteria:**
-   [ ] New users can successfully register and log in.
-   [ ] Existing users can securely log in and access their dashboard.
-   [ ] Users can view and update their profile information.
-   [ ] Users can search for and find other registered users.
-   [ ] User online/offline status is accurately displayed.

**User Stories:**
-   **US-001:** Register an account
  - **As a** new user
  - **I want to** register an account with my email and password
  - **So that** I can start using the messaging app.
  - **Acceptance Criteria:**
    - [ ] The system validates required inputs (unique email, strong password).
    - [ ] My account is created successfully.
    - [ ] I am automatically logged in or redirected to the login page upon successful registration.
  - **Story Points:** 5
  - **Priority:** High

-   **US-002:** Log in securely
  - **As a** registered user
  - **I want to** log in to my account securely
  - **So that** I can access my chats and profile.
  - **Acceptance Criteria:**
    - [ ] I can enter my registered email and password.
    - [ ] Upon valid credentials, I am authenticated and granted access.
    - [ ] Upon invalid credentials, I receive an appropriate error message.
    - [ ] My session is secured using JWT.
  - **Story Points:** 3
  - **Priority:** High

-   **US-003:** See my online/offline status
  - **As a** user
  - **I want to** see my online/offline status, and have others see it
  - **So that** others know my availability for communication.
  - **Acceptance Criteria:**
    - [ ] My status is shown as 'Online' when I am active in the app.
    - [ ] My status changes to 'Offline' when I log out or am inactive.
    - [ ] I can see the online/offline status of other users in my contact list/conversation list.
  - **Story Points:** 5
  - **Priority:** High

-   **US-004:** Update my profile information
  - **As a** user
  - **I want to** update my profile information (e.g., username, optional profile picture)
  - **So that** I can personalize my identity in the app.
  - **Acceptance Criteria:**
    - [ ] I can navigate to a profile settings page.
    - [ ] I can modify my username (if allowed).
    - [ ] I can upload/change my profile picture (if implemented, Phase 3).
    - [ ] Changes are saved and reflected in my profile and to other users.
  - **Story Points:** 5
  - **Priority:** Medium

-   **US-013:** Search for other users
  - **As a** user
  - **I want to** search for other users by username or email
  - **So that** I can find people to chat with.
  - **Acceptance Criteria:**
    - [ ] I can enter a search query in a dedicated search bar.
    - [ ] The system returns a list of matching users in real-time (or near real-time).
    - [ ] I can initiate a new conversation directly from the search results.
  - **Story Points:** 5
  - **Priority:** High

### Epic 2: One-to-One Real-time Messaging (MVP)
**Epic Description:** Enable users to engage in instant, private conversations with another user, including sending and receiving text messages and viewing conversation history.
**Business Value:** Provides the core utility of a messaging application, facilitating direct and efficient communication between individuals, which is the primary value proposition of the MVP.
**Acceptance Criteria:**
-   [ ] Users can view a list of their one-to-one conversations.
-   [ ] Users can send and receive text messages instantly.
-   [ ] Chat history is accurately displayed and persistent.

**User Stories:**
-   **US-005:** View a list of existing conversations
  - **As a** user
  - **I want to** view a list of my existing conversations
  - **So that** I can quickly resume chatting with individuals.
  - **Acceptance Criteria:**
    - [ ] A list of my 1:1 conversations is displayed on the main chat screen.
    - [ ] Each conversation entry shows the name of the other participant.
    - [ ] Each conversation entry shows a preview of the last message exchanged.
  - **Story Points:** 5
  - **Priority:** High

-   **US-006:** Send a real-time text message
  - **As a** user
  - **I want to** send a real-time text message to another user
  - **So that** I can communicate instantly.
  - **Acceptance Criteria:**
    - [ ] I can type a message in an active chat window.
    - [ ] I can press 'Send' or 'Enter' to dispatch the message.
    - [ ] The message appears in my chat window immediately after sending.
    - [ ] The message is delivered to the recipient's active chat window in real-time.
  - **Story Points:** 8
  - **Priority:** High

-   **US-007:** Receive real-time text messages
  - **As a** user
  - **I want to** receive real-time text messages from other users
  - **So that** I can engage in conversations.
  - **Acceptance Criteria:**
    - [ ] Incoming messages appear instantly in my active chat window.
    - [ ] Messages are correctly attributed to the sender.
  - **Story Points:** 8
  - **Priority:** High

-   **US-008:** View chat history
  - **As a** user
  - **I want to to** see my chat history with another user
  - **So that** I can recall past conversations.
  - **Acceptance Criteria:**
    - [ ] When I open a 1:1 chat, previous messages are loaded and displayed chronologically.
    - [ ] The chat history loads efficiently, even for long conversations.
    - [ ] Messages are persisted and available across sessions.
  - **Story Points:** 8
  - **Priority:** High

### Epic 3: Group Chat Capabilities (Phase 3)
**Epic Description:** Extend the messaging functionality to allow users to create and participate in multi-person conversations.
**Business Value:** Enhances collaboration and allows for broader communication, increasing the utility and stickiness of the application.
**Acceptance Criteria:**
-   [ ] Users can create new group chats.
-   [ ] Group administrators can manage group members.
-   [ ] Users can send and receive messages within group chats.
-   [ ] Group chat history is accessible and persistent.

**User Stories:**
-   **US-009:** Create a new group chat
  - **As a** user
  - **I want to** create a new group chat with selected users
  - **So that** I can communicate with multiple people at once.
  - **Acceptance Criteria:**
    - [ ] I can select multiple users to form a group.
    - [ ] I can name the group chat.
    - [ ] The group chat is created, and all selected users are added as members.
  - **Story Points:** 8
  - **Priority:** Medium

-   **US-010:** Add/remove members from a group chat
  - **As a** group administrator
  - **I want to** add or remove members from a group chat I administer
  - **So that** I can manage group participation.
  - **Acceptance Criteria:**
    - [ ] Only group administrators can add new members to a group.
    - [ ] Only group administrators can remove existing members from a group.
    - [ ] All group members are notified of member changes.
  - **Story Points:** 8
  - **Priority:** Medium

-   **US-011:** Send a text message to a group
  - **As a** user
  - **I want to** send a text message to a group
  - **So that** I can communicate with all group members simultaneously.
  - **Acceptance Criteria:**
    - [ ] I can compose and send a message within an active group chat.
    - [ ] The message is delivered to all active members of the group in real-time.
  - **Story Points:** 5
  - **Priority:** Medium

-   **US-012:** View group message history
  - **As a** user
  - **I want to** view the message history of a group chat
  - **So that** I can catch up on past conversations with the group.
  - **Acceptance Criteria:**
    - [ ] When I open a group chat, previous messages are loaded and displayed chronologically.
    - [ ] The history loads efficiently for groups with many messages and members.
  - **Story Points:** 5
  - **Priority:** Medium

### Epic 4: Enhanced Communication Features (Phase 3)
**Epic Description:** Introduce advanced features like notifications and media sharing to enrich the user's communication experience.
**Business Value:** Improves user engagement by ensuring important messages are not missed and by enabling more expressive and informative conversations.
**Acceptance Criteria:**
-   [ ] Users receive real-time notifications for new messages.
-   [ ] Users can share various media types within chats.

**User Stories:**
-   **US-014:** Receive new message notification
  - **As a** user
  - **I want to** receive a real-time notification when I get a new message
  - **So that** I don't miss important communications, even if I'm not actively in the chat.
  - **Acceptance Criteria:**
    - [ ] A visual (e.g., badge count) and/or audible notification is triggered for new messages when the app is in the background or the chat is not open.
    - [ ] Clicking the notification takes me to the relevant chat.
  - **Story Points:** 5
  - **Priority:** Medium

-   **US-015:** Share images/files in a chat
  - **As a** user
  - **I want to** share images/files in a chat
  - **So that** I can easily exchange visual or document content with other users.
  - **Acceptance Criteria:**
    - [ ] I can select an image or file from my device to upload.
    - [ ] The selected media is uploaded to storage.
    - [ ] The media is displayed appropriately within the chat window (e.g., image thumbnail, file link).
    - [ ] Other users can view/download the shared media.
  - **Story Points:** 13
  - **Priority:** Medium

## 9. User Interface Requirements
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*   **UI Framework Consistency:** Adhere strictly to the VMware Clarity Design System for all UI components, styling, and visual language to ensure a consistent and enterprise-grade look and feel. (Referenced: `analysis_document.md` Project Overview, `tech_stack_document.md` Frontend Technologies)
*   **Responsiveness:** The application's UI must be fully responsive, adapting seamlessly to various screen sizes, from mobile devices to large desktop monitors (NFR-PM-005).
*   **Intuitive Layout:** Provide a clear and easy-to-navigate layout, including a distinct area for conversation lists, active chat windows, and user profiles. (Referenced: `analysis_document.md` User Requirements).
*   **Chat Experience:** The chat interface should feature:
    *   A prominent message input field.
    *   Clear display of sender, message content, and timestamp.
    *   Visual indicators for online status and potentially typing status.
    *   Efficient scrolling for message history.
*   **Accessibility:** Ensure the UI components meet basic accessibility standards (e.g., keyboard navigation, screen reader compatibility), as promoted by the Clarity Design System.
*   **Error Feedback:** Provide clear and user-friendly error messages and feedback for actions like failed login, message sending errors, etc.

## 10. Technical Requirements
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*   **Frontend (Angular Clarity):**
    *   Extend the provided Angular Clarity boilerplate with new feature modules (Auth, User, Chat).
    *   Utilize Angular's HttpClient for REST API communication and a dedicated WebSocket service for real-time data.
    *   Implement RxJS for reactive programming and efficient state management. (Referenced: `tech_stack_document.md` Frontend Technologies).
*   **Backend (Python FastAPI):**
    *   Develop a Python FastAPI application for RESTful APIs (authentication, user management, conversation management, message history retrieval).
    *   Implement a separate WebSocket endpoint within FastAPI/Starlette to handle real-time messaging and user presence.
    *   Utilize SQLAlchemy for ORM interactions with PostgreSQL and Alembic for database migrations. (Referenced: `tech_stack_document.md` Backend Technologies).
*   **Database (PostgreSQL & Redis):**
    *   PostgreSQL as the primary relational database for persistent storage of users, conversations, and messages.
    *   Redis for real-time user presence, caching, and a Pub/Sub mechanism to scale WebSocket services. (Referenced: `tech_stack_document.md` Database Technologies).
*   **Security:**
    *   Implement JWT for secure API and WebSocket authentication.
    *   Ensure TLS/SSL encryption for all network communications (HTTPS/WSS).
    *   Implement server-side input validation and data sanitization. (Referenced: `architecture_document.md` Security Architecture).
*   **Deployment:**
    *   Containerize all services using Docker.
    *   Use Docker Compose for local development and potential staging environments.
    *   Design for Kubernetes/ECS deployment in production for horizontal scaling. (Referenced: `tech_stack_document.md` Infrastructure, `architecture_document.md` Scalability Considerations).
*   **API Design:** Follow a RESTful pattern for stateless operations and a WebSocket event-driven pattern for real-time communication. (Referenced: `architecture_document.md` API Design).

## 11. Success Metrics & KPIs
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*   **User Registration Rate:** Percentage of visitors who complete registration.
*   **Daily Active Users (DAU) / Monthly Active Users (MAU):** Number of unique users interacting with the app daily/monthly, a key indicator of product stickiness and value.
*   **Average Message Latency:** Average time taken for a message to be delivered and displayed (target < 500ms) - directly measures NFR-PM-001.
*   **Backend API Response Time:** Average response time for core API endpoints (target < 200ms) - also related to NFR-PM-001.
*   **Uptime/Availability:** Percentage of time the core services are operational (target 99.9%) - directly measures NFR-PM-004.
*   **User Retention Rate:** Percentage of users who return to the app after a specified period (e.g., 7-day, 30-day) - indicates long-term user satisfaction.
*   **Error Rate:** Frequency of critical errors in frontend and backend (target < 0.1%) - indicates system stability and reliability.
*   **Feature Adoption:** (Post-MVP) Percentage of users utilizing group chat, media sharing, or notification features after their release.

## 12. Risk Assessment
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*   **Scalability Challenges (High):** Real-time messaging can be resource-intensive. High concurrent user numbers or message volumes could strain the system. (Identified in `analysis_document.md` and `architecture_document.md`)
    *   **Mitigation:** Microservices architecture with stateless design; horizontal scaling for all backend services and WebSocket Gateways; leveraging Redis Pub/Sub for efficient message fan-out; database read replicas; load balancing.
*   **Performance Bottlenecks (High):** Ensuring low message latency and responsive UI across varying network conditions is critical. (Identified in `analysis_document.md`)
    *   **Mitigation:** Extensive caching (Redis); optimized database queries with proper indexing; efficient WebSocket protocol usage; frontend performance optimization (lazy loading, AOT compilation); robust monitoring for early detection.
*   **Security Vulnerabilities (High):** Authentication bypasses, data breaches, message interception are severe risks. (Identified in `analysis_document.md` and `architecture_document.md`)
    *   **Mitigation:** JWT with refresh token mechanism; strong password hashing; strict TLS/SSL for all communications; comprehensive input validation; RBAC for authorization; regular security audits; secure secret management.
*   **Integration Complexity (Medium):** Integrating a new Python backend with an existing Angular Clarity boilerplate, especially with real-time WebSockets, can be challenging. (Identified in `analysis_document.md`)
    *   **Mitigation:** Clear API contracts (REST & WebSocket); phased integration starting with MVP; thorough testing of frontend-backend communication; well-defined module boundaries.
*   **Scope Creep (Medium):** Tendency to add more features beyond the MVP, delaying core functionality delivery. (Identified in `analysis_document.md`)
    *   **Mitigation:** Strict adherence to MVP definition for Phase 2; clear prioritization of Epics/User Stories; frequent communication with stakeholders about scope; timeboxing feature development.
*   **Database Performance (Medium):** Unoptimized queries or large data volumes could lead to slow message history retrieval or user lookups.
    *   **Mitigation:** Strategic indexing on `conversation_id`, `sender_id`, `sent_at`; pagination for history retrieval; database connection pooling; consider database partitioning for extreme scale.

## 13. Timeline & Milestones
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This project will follow a phased approach, aligning with the `analysis_document.md` updates, with continuous iteration within each phase. (Estimated durations are approximate and subject to team velocity and complexity).

*   **Phase 1: Discovery & Architecture (Completed - Initial Stage)**
    *   **Goal:** Establish foundational project understanding and technical blueprints.
    *   **Deliverables:** `analysis_document.md`, `architecture_document.md`, `tech_stack_document.md`, Initial `prd_document.md`.
*   **Phase 2: Core Messaging MVP Development (Current Focus - Est. 8-12 weeks)**
    *   **Goal:** Deliver a fully functional 1:1 messaging system with secure authentication and message persistence.
    *   **Key Milestones:**
        *   **M2.1:** User Auth & Profile Backend APIs (Register, Login, Profile CRUD, User Search)
        *   **M2.2:** Frontend Auth & Profile UI Integration
        *   **M2.3:** Core 1:1 Messaging Backend (Message persistence, Real-time via WebSockets)
        *   **M2.4:** Frontend 1:1 Chat UI Integration (Conversation list, Chat window, Send/Receive, History display)
        *   **M2.5:** Basic User Presence (Online/Offline status)
        *   **M2.6:** Dockerization for MVP components & local dev setup.
*   **Phase 3: Feature Expansion & Quality Assurance (Est. 6-10 weeks)**
    *   **Goal:** Implement advanced messaging features and ensure high quality.
    *   **Key Milestones:**
        *   **M3.1:** Group Chat Backend & Frontend Integration
        *   **M3.2:** Notification System Implementation
        *   **M3.3:** Media Sharing Backend & Frontend Integration
        *   **M3.4:** Comprehensive Testing (Unit, Integration, E2E, Performance, Security)
*   **Phase 4: Deployment Readiness & Operations (Est. 4-6 weeks)**
    *   **Goal:** Prepare for production deployment and establish operational excellence.
    *   **Key Milestones:**
        *   **M4.1:** CI/CD Pipeline Setup (Build, Test, Deploy)
        *   **M4.2:** Production Environment Configuration (Kubernetes/ECS deployment, Nginx)
        *   **M4.3:** Monitoring & Logging Stack Implementation (Prometheus, Grafana, Loki/ELK)
        *   **M4.4:** Security Hardening & Penetration Testing

## 14. Dependencies & Assumptions
### Update: 2025-10-10T04:22:00.000000

**Dependencies:**
*   **Existing Angular Clarity Boilerplate:** Frontend development is dependent on the stable and functional base provided by the boilerplate. No breaking changes or regressions should be introduced to the core boilerplate structure. (Referenced: `analysis_document.md` Constraints)
*   **External Cloud Services:** Availability and configuration of cloud services (e.g., PostgreSQL, Redis, Object Storage like AWS S3 for Phase 3) are critical.
*   **Team Skills:** Availability of developers proficient in Angular, TypeScript, Python, FastAPI, WebSockets, PostgreSQL, Docker, and CI/CD practices.

**Assumptions:**
*   **API Stability:** Backend API contracts (REST and WebSocket) will remain stable once defined for each phase, minimizing refactoring on the frontend.
*   **Development Environment:** Developers have access to suitable development environments (Node.js, Python, Docker, IDEs).
*   **Performance Expectations:** Initial performance targets are achievable with the chosen tech stack and architecture; significant re-architecture will not be required for the MVP.
*   **Security Best Practices:** The development team will adhere to security best practices throughout the development lifecycle (e.g., secure coding, regular dependency updates).
*   **Feedback Loop:** Timely feedback from stakeholders will be available to facilitate iterative development and prioritization decisions.



---

## PRD UPDATE - 2025-10-10 04:24:22

### Update: 2025-10-10T04:30:00.000000

## 6. Functional Requirements

*(No new top-level functional requirements added, detailed in Epic Stories below.)*

## 7. Non-Functional Requirements
### Update: 2025-10-10T04:30:00.000000
*   **NFR-PM-003: Security:** ... Furthermore, a strict **Content Security Policy (CSP)** must be implemented for the frontend to mitigate XSS attacks. Rate limiting will be applied to authentication and registration endpoints to prevent brute-force attacks. (Referenced: `architecture_document.md` Security Architecture Enhancements).

## 8. Epic Stories
### Update: 2025-10-10T04:30:00.000000

### Epic 2: One-to-One Real-time Messaging (MVP)
**User Stories:**
-   **US-006:** Send a real-time text message
  - **Acceptance Criteria:**
    - [ ] The message content does not exceed 2000 characters.
    - [ ] ... (existing criteria)

### Epic 3: Group Chat Capabilities (Phase 3)
**User Stories:**
-   **US-009:** Create a new group chat
  - **Acceptance Criteria:**
    - [ ] I can select multiple users to form a group (minimum of 2 users excluding myself).
    - [ ] ... (existing criteria)

-   **US-011:** Send a text message to a group
  - **Acceptance Criteria:**
    - [ ] The message content does not exceed 2000 characters.
    - [ ] ... (existing criteria)

### Epic 4: Enhanced Communication Features (Phase 3)
**User Stories:**
... (existing user stories US-014, US-015)

-   **US-016:** See when my message has been read
  - **As a** user
  - **I want to** see when my message has been read by the recipient(s) in a conversation
  - **So that** I know my message has been acknowledged.
  - **Acceptance Criteria:**
    - [ ] A visual indicator (e.g., a double-tick or an 'Read' status) appears next to my sent message once all recipients in a 1:1 chat have viewed it.
    - [ ] For group chats, a visual indicator shows how many members have read the message, or who specifically has read it upon hovering/clicking.
  - **Story Points:** 8
  - **Priority:** Medium

## 10. Technical Requirements
### Update: 2025-10-10T04:30:00.000000
*   **Security:**
    *   ... (existing points)
    *   Implement **Content Security Policy (CSP)** headers on the frontend to prevent XSS attacks.
    *   Apply API rate limiting at the Nginx and/or FastAPI level for authentication and registration endpoints. (Referenced: `architecture_document.md` Security Architecture Enhancements).
*   **Database (PostgreSQL & Redis):**
    *   ... (existing points)
    *   Implement strategic indexing on `Message` (`conversation_id`, `sender_id`, `sent_at`), `User` (`username`, `email`), and `ConversationParticipant` (`user_id`, `conversation_id`) tables to optimize query performance for message history and user lookups. (Referenced: `architecture_document.md` Data Architecture Refinement).

## 12. Risk Assessment
### Update: 2025-10-10T04:30:00.000000
*   **Database Performance (Medium):** ...
    *   **Mitigation (Additional):** Consider database read replicas for read-heavy operations, and explore partitioning strategies for the `Message` table in future phases to manage extreme data growth, directly supporting NFR-PM-002 (Scalability). (Referenced: `architecture_document.md` Data Architecture Refinement).
*   **Security Vulnerabilities (High):** ...
    *   **Mitigation (Additional):** Implement a strict Content Security Policy (CSP) on the frontend; utilize secure environment variable management in production. (Referenced: `architecture_document.md` Security Architecture Enhancements).



---

## PRD UPDATE - 2025-10-10 04:25:14



## 6. Functional Requirements
*Updated: 2025-10-10T04:22:00*
*   **Message Constraints:**
    *   FR-019: Message Length Limit: Text messages will be limited to a maximum of 1024 characters to ensure system efficiency and prevent abuse, as per business rules in `analysis_document.md`.

## 7. Non-Functional Requirements
*Updated: 2025-10-10T04:22:00*
*   **Performance:**
    *   NFR-001 (Refined): Message Latency: Messages should be delivered within **200ms** for 95% of messages under normal load (up to 1,000 concurrent users), and within 500ms for 99% of messages.
    *   NFR-002 (Refined): Concurrent Users: The system shall support at least 1,000 concurrent users (MVP), scalable to **5,000+** in Phase 2, and 10,000+ in future phases, with consistent performance.
    *   NFR-003 (Refined): Response Time (API): REST API endpoints should respond within **150ms** for 90% of requests, and 300ms for 99% of requests.
*   **Security:**
    *   NFR-004 (Refined): Authorization: Implement Role-Based Access Control (RBAC) to ensure users only access resources and perform actions for which they have explicit permissions (e.g., `member` vs. `admin` in group chats), and enforce resource ownership checks for individual messages/conversations.
    *   NFR-005 (Refined): Data Encryption: All data in transit (HTTP/WSS) must be encrypted using TLS/SSL. Passwords must be hashed and salted at rest using `bcrypt`. Consider database-level encryption for sensitive data at rest for future enhancements.
    *   NFR-006 (Added): API Rate Limiting: Implement rate limiting on authentication and registration endpoints to prevent brute-force attacks and abuse (as identified in `architecture_document.md` and `tech_stack_document.md`).
    *   NFR-007 (Added): Content Security Policy (CSP): Implement a strict CSP for the frontend to mitigate Cross-Site Scripting (XSS) attacks.
*   **Scalability:**
    *   NFR-008 (Refined): Horizontal Scaling: All backend services (Auth, User, Chat, WebSocket) must be designed as stateless entities, allowing them to be scaled horizontally by adding more instances behind a load balancer. Redis Pub/Sub will facilitate message distribution across scaled WebSocket instances.
    *   NFR-009 (Refined): Database Scalability: PostgreSQL will be configured for high availability with master-replica (read-only) setups to distribute read load. Redis cluster mode will be used for horizontal scaling of real-time data and pub/sub. Future consideration for sharding `Message` table for extreme volumes.
*   **Reliability:**
    *   NFR-010 (Refined): Message Delivery Guarantee: Messages sent must be reliably delivered and persisted, using Redis Streams/Lists to buffer messages for offline users and ensure at-least-once delivery, even in case of temporary network disruptions.
    *   NFR-011 (Added): Automated Backups: Regular automated backups of the PostgreSQL database will be implemented to ensure data durability and recovery capabilities (as per `architecture_document.md`).
*   **Maintainability:**
    *   NFR-012 (Refined): Monitoring & Logging: Implement comprehensive monitoring (Prometheus, Grafana) and centralized logging (Loki/ELK) across all application layers (frontend, backend, database, Redis) for proactive issue identification and performance analysis.
    *   NFR-013 (Added): Error Tracking: Integrate real-time error tracking (e.g., Sentry) for both frontend and backend to quickly identify and resolve application errors.

## 10. Technical Requirements
*Updated: 2025-10-10T04:22:00*
*   **Frontend (Angular Clarity):**
    *   Utilize a custom Angular service leveraging the native `WebSocket` API (or `ngx-web-socket` wrapper) for real-time communication, handling connection management, sending events, and receiving messages.
    *   Ensure secure handling of JWTs for authentication, storing them securely (e.g., HttpOnly cookies, not local storage) with both REST and WebSocket connections, and implementing a token refresh mechanism.
    *   Employ RxJS for managing complex asynchronous data streams and state within components and services.
    *   Configure a strict Content Security Policy (CSP) to enhance frontend security.
*   **Backend (Python FastAPI):**
    *   Develop multiple FastAPI services (Authentication, User, Conversation, Message) for a microservices-aligned architecture.
    *   Implement a dedicated FastAPI/Starlette WebSocket service for managing persistent client connections, real-time message broadcasting, and user presence updates.
    *   Utilize SQLAlchemy with Alembic for database migrations and ORM interactions with PostgreSQL, ensuring robust and version-controlled schema evolution.
    *   Implement JWT-based authentication using `python-jose` or `PyJWT` for token generation/validation, and `bcrypt` for secure password hashing.
    *   Expose comprehensive OpenAPI/Swagger UI documentation for all REST API endpoints.
*   **Real-time Communication Layer:**
    *   Employ a Redis instance for **Pub/Sub functionality** to enable efficient and scalable message broadcasting across horizontally scaled WebSocket service instances.
    *   Leverage **Redis Streams or Lists** to temporarily store messages for users who are offline or disconnected, ensuring guaranteed message delivery upon reconnection.
    *   Use Redis for fast, in-memory storage and retrieval of user presence status (online/offline/away).
*   **Database (PostgreSQL):**
    *   Implement robust indexing on key tables, particularly `Message` (`conversation_id`, `sender_id`, `sent_at`) and `ConversationParticipant` (`user_id`, `conversation_id`), to optimize query performance for chat history and user lookups.
    *   Configure PostgreSQL with read replicas to distribute read load, enhancing scalability for data retrieval operations.
    *   Actively update `ConversationParticipant.last_read_message_id` to enable read receipts and unread message indicators.
*   **Caching:**
    *   Utilize Redis for caching frequently accessed, less volatile data (e.g., user profiles, conversation metadata) to reduce database load and improve API response times.
*   **Deployment & Infrastructure:**
    *   Containerize all services (Frontend, Backend API, WebSocket, Redis, PostgreSQL) using Docker for consistent development and production environments.
    *   Provide `docker-compose.yml` for simplified local development and testing of the multi-service application.
    *   For production, plan for deployment using container orchestration platforms like Kubernetes or AWS ECS/Fargate to enable horizontal scaling, high availability, and automated management of services.
    *   Configure Nginx as a reverse proxy and load balancer to serve the frontend, route API requests, manage WebSocket connections, and handle SSL termination and API rate limiting.
*   **Monitoring & Logging:**
    *   Integrate Prometheus for collecting metrics from all services and Grafana for creating comprehensive dashboards to visualize system performance and health.
    *   Implement a centralized logging solution (e.g., Loki with Promtail, or ELK stack) to aggregate and analyze logs from all containers for debugging and operational insights.
    *   Integrate Sentry for real-time error tracking and alerts across the stack.
*   **API Contracts:** Define clear and consistent RESTful API endpoints and WebSocket event formats (JSON payloads) for seamless frontend-backend integration, documented automatically by FastAPI.
*   **Background Processing (Phase 2):** Introduce a background task queue (e.g., Celery with Redis as broker) for asynchronous processing of computationally intensive tasks, such as media resizing/processing or complex notification delivery.

## 12. Risk Assessment
*Updated: 2025-10-10T04:22:00*
*(Building upon `analysis_document.md`, `io8codermaster_plan.md`, `architecture_document.md`, and `tech_stack_document.md`)*

1.  **Scalability Challenges (High):**
    *   **Risk:** Real-time messaging can be resource-intensive, leading to performance degradation with increased concurrent users if not architected and implemented correctly.
    *   **Mitigation:**
        *   Implement stateless backend microservices for effective horizontal scaling, ensuring each component can scale independently.
        *   Utilize Redis Pub/Sub for WebSocket message distribution across multiple WebSocket service instances.
        *   Employ efficient database indexing on `Message` and `ConversationParticipant` tables, and consider PostgreSQL read replicas for read-heavy operations.
        *   Leverage Redis cluster mode for horizontally scaling real-time data storage (presence) and Pub/Sub capabilities.
        *   Regularly perform load testing and performance benchmarking against defined NFR-001/002 targets.
2.  **Performance & Latency (High):**
    *   **Risk:** High message latency or slow UI response times can severely degrade user experience, leading to user dissatisfaction and churn.
    *   **Mitigation:**
        *   Optimize WebSocket message processing and broadcasting logic, ensuring minimal overhead.
        *   Minimize direct database queries for real-time operations by leveraging Redis for user presence and caching frequently accessed data.
        *   Implement efficient frontend rendering strategies within Angular to reduce UI lag.
        *   Continuously monitor network performance, optimize payload sizes, and utilize monitoring tools (Prometheus/Grafana) to identify and address bottlenecks.
3.  **Security Vulnerabilities (High):**
    *   **Risk:** User data breaches, unauthorized access, communication eavesdropping, or common web vulnerabilities (XSS, SQLi) could erode user trust and lead to compliance issues.
    *   **Mitigation:**
        *   Implement robust JWT authentication with token expiration and refresh mechanisms, and enforce RBAC authorization for resource access.
        *   Enforce TLS/SSL (HTTPS/WSS) for all communications. Securely hash passwords using bcrypt.
        *   Perform comprehensive input validation on both frontend and backend to prevent injection attacks and other vulnerabilities.
        *   Implement API rate limiting on critical endpoints (e.g., login, registration) at both the Nginx reverse proxy and application level.
        *   Configure a strict Content Security Policy (CSP) for the frontend. Securely manage environment variables and secrets.
        *   Conduct regular security audits, vulnerability assessments, and penetration testing throughout the development lifecycle.
4.  **Integration Complexity (Medium):**
    *   **Risk:** Integrating a new Python FastAPI backend and real-time layer with an existing Angular Clarity boilerplate, along with various infrastructure components (PostgreSQL, Redis, Nginx), might lead to unforeseen compatibility issues, development overhead, or delays.
    *   **Mitigation:**
        *   Define clear and detailed API contracts (REST and WebSocket event formats) upfront and enforce strict adherence by both frontend and backend teams.
        *   Maintain modularity on both frontend and backend to isolate changes and reduce cascading effects.
        *   Conduct frequent, automated integration testing between frontend and backend services.
        *   Utilize Docker Compose for consistent local development and staging environments, streamlining the integration process.
5.  **Scope Creep (Medium):**
    *   **Risk:** Uncontrolled addition of feature requests beyond the MVP could delay critical functionalities, increase project costs, and impact delivery timelines for the core messaging experience.
    *   **Mitigation:**
        *   Strictly adhere to the defined MVP scope (Phase 2 features) for initial delivery, clearly categorizing future features into subsequent phases (Phase 3, Phase 4).
        *   Prioritize backlog items based on immediate business value and MVP goals using an Agile framework.
        *   Implement a robust change management process for new feature requests, requiring thorough evaluation against project scope and objectives.
        *   Regularly communicate scope and prioritization decisions to all stakeholders to ensure alignment.

## 13. Timeline & Milestones
*Updated: 2025-10-10T04:22:00*
*(Aligned with `analysis_document.md`'s "Update: Project Phases and Milestones" and `tech_stack_document.md` operational details)*

**Phase 1: Discovery & Architecture (Completed)**
*   **Output:** Detailed `analysis_document.md`, `architecture_document.md`, `tech_stack_document.md`, and this comprehensive `prd_document.md`.

**Phase 2: Core Messaging MVP Development (Target: 8-10 weeks)**
*   **Milestone 1: Foundational Services & Authentication (Weeks 1-3)**
    *   **Backend:** Develop and test User Authentication Service (registration, login, JWT issuance/validation), User Profile Management, and initial PostgreSQL database schema for Users/Conversations/Messages. Implement API rate limiting.
    *   **Frontend:** Integrate Angular Auth Module with Clarity UI for user registration/login. Implement secure JWT storage and retrieval. Basic User Profile view.
*   **Milestone 2: Real-time 1:1 Messaging & Persistence (Weeks 4-7)**
    *   **Backend:** Develop Message Service (persistence), WebSocket Service (real-time delivery using FastAPI/Starlette), integrate Redis for Pub/Sub and user presence. Implement message buffering for offline users (Redis Streams/Lists).
    *   **Frontend:** Develop Angular Chat Module (1:1 chat UI, message input, real-time sending/receiving messages, displaying paginated history). Integrate user presence display.
*   **Milestone 3: MVP Integration, QA & Local Deployment (Weeks 8-10)**
    *   Full end-to-end integration of frontend and backend. Implement unit and integration tests (Jest/Pytest). Initial performance testing for latency and concurrent users. Configure `docker-compose.yml` for consistent local development across all services. Set up basic monitoring for local environment.

**Phase 3: Feature Expansion & Quality Assurance (Target: 6-8 weeks, starting after MVP)**
*   **Milestone 4: Group Chat & UI Enhancements (Weeks 1-3)**
    *   **Backend:** Extend Conversation Service for Group Chat management (creation, member add/remove), Message Service for group messaging.
    *   **Frontend:** Develop Group Chat UI, enhance conversation list to differentiate 1:1 and group chats.
*   **Milestone 5: Notifications & Media Sharing (Weeks 3-5)**
    *   **Backend:** Develop Notification Service, integrate with object storage (AWS S3/GCS) for File Storage Service, implement background task queue (Celery/Redis) for media processing.
    *   **Frontend:** Implement in-app notification display, integrate media upload/display capabilities in chat.
*   **Milestone 6: Comprehensive Testing & Optimization (Weeks 5-8)**
    *   Conduct full E2E testing (Cypress/Playwright), security audits, advanced load testing, and comprehensive performance optimization across all features.
    *   Extensive bug fixing. Refine monitoring dashboards (Grafana) and logging queries (Loki/ELK).

**Phase 4: Deployment Readiness & Operations (Target: 2-3 weeks, after Feature Expansion)**
*   **Milestone 7: CI/CD & Production Infrastructure Setup (Weeks 1-2)**
    *   Set up robust CI/CD pipelines (GitHub Actions/GitLab CI) for automated linting, testing, container image building, vulnerability scanning, and deployment to staging environments.
    *   Configure production-grade infrastructure on cloud (e.g., Kubernetes/ECS, PostgreSQL with read replicas, Redis Cluster, Nginx load balancer). Establish secure environment variable management.
*   **Milestone 8: Monitoring, Logging & Production Deployment (Weeks 2-3)**
    *   Implement comprehensive monitoring (Prometheus/Grafana), centralized logging (Loki/ELK), and error tracking (Sentry) for production. Configure alerts for critical issues.
    *   Automate database backups. Final deployment of the application to the production environment, followed by post-deployment verification and continuous operational support.

## 14. Dependencies & Assumptions
*Updated: 2025-10-10T04:22:00*
**Dependencies:**
*   **Angular Clarity Boilerplate:** Continued stability and extensibility of the provided boilerplate is critical for frontend development.
*   **Backend Services:** All defined backend microservices (Auth, User, Conversation, Message, WebSocket, Notification, File Storage) must be developed and stable.
*   **Database Infrastructure:** Reliable and scalable PostgreSQL and Redis instances (including Pub/Sub and Streams) are provisioned and accessible.
*   **Cloud Services:** Access to object storage (e.g., AWS S3) for media sharing (Phase 2).
*   **Developer Skillset:** Availability of development team proficient in Angular, TypeScript, Python, FastAPI, WebSockets, Docker, PostgreSQL, Redis, and cloud deployment practices.
*   **Nginx Configuration:** Correct Nginx setup for routing, load balancing, and SSL termination for both REST and WebSocket traffic.

**Assumptions:**
*   The existing Angular Clarity boilerplate is stable and extensible without requiring significant refactoring or introducing breaking changes.
*   The project team has access to necessary development tools, cloud infrastructure, and security resources throughout the project lifecycle.
*   Real-time performance metrics (NFR-001) can be achieved with the chosen technology stack under expected load and concurrent users (NFR-002).
*   Security requirements (NFR-004 to NFR-007) are clearly defined, will be continuously reviewed, and validated through security audits.
*   Stakeholders are fully aligned on the MVP scope and phased rollout strategy, minimizing scope changes during active development phases.
*   Third-party libraries and services used (e.g., `bcrypt`, `python-jose`, Sentry, Prometheus) maintain their functionality and support.

