# Product Requirements Document: Stock Listing Application

## 1. Overview

The Stock Listing Application is a web-based platform that provides users with a comprehensive view of available stocks and shares in the market. The application serves as a centralized repository for stock information, allowing users to browse, search, and view detailed information about various publicly traded companies. This system is designed to deliver real-time or near-real-time stock data in an accessible and user-friendly interface.

## 2. User Roles

### 2.1 Anonymous User (Guest)
- View the list of all available stocks
- Search and filter stocks by various criteria
- View basic stock details
- Access the application without authentication

### 2.2 Registered User
- All permissions of Anonymous User
- Save favorite/watchlist stocks
- View personalized stock recommendations
- Access historical viewing history
- Receive notifications about stock updates (future enhancement)

### 2.3 Administrator
- All permissions of Registered User
- Add new stocks to the system
- Edit existing stock information
- Delete or archive stocks
- Manage user accounts
- View system analytics and usage statistics
- Configure system settings
- Manage stock categories and sectors

### 2.4 Data Manager
- All permissions of Registered User
- Add and update stock information
- Import bulk stock data
- Verify and validate stock information
- Cannot delete stocks or manage users

## 3. Core Entities

### 3.1 Stock
The primary entity representing a publicly traded company's shares.
- **Attributes**: Stock ID, ticker symbol, company name, current price, opening price, closing price, high price, low price, volume, market capitalization, sector, industry, exchange, currency, last updated timestamp, description, logo URL, website URL, country, IPO date, status (active/inactive)

### 3.2 User
Represents individuals who interact with the system.
- **Attributes**: User ID, email, password hash, first name, last name, role, registration date, last login date, status (active/inactive/suspended), profile picture URL, preferences

### 3.3 Watchlist
A collection of stocks that a user wants to monitor.
- **Attributes**: Watchlist ID, user ID, name, description, created date, last modified date, is default, sort order

### 3.4 WatchlistItem
Individual stocks within a watchlist.
- **Attributes**: Watchlist item ID, watchlist ID, stock ID, added date, notes, sort order

### 3.5 Sector
Industry sector classification for stocks.
- **Attributes**: Sector ID, name, description, icon/image URL, display order

### 3.6 Exchange
Stock exchange where stocks are traded.
- **Attributes**: Exchange ID, name, code, country, timezone, trading hours, currency, website URL, description

### 3.7 StockHistory
Historical price data for stocks.
- **Attributes**: History ID, stock ID, date, open price, close price, high price, low price, volume, adjusted close price

### 3.8 UserActivity
Tracks user interactions with stocks.
- **Attributes**: Activity ID, user ID, stock ID, activity type (view/search/favorite), timestamp, session ID

### 3.9 SystemConfiguration
Application-wide settings and configurations.
- **Attributes**: Config ID, key, value, data type, description, last modified date, modified by user ID

## 4. Entity Relationships

### 4.1 Stock Relationships
- **Stock → Sector**: Many-to-One (many stocks belong to one sector)
- **Stock → Exchange**: Many-to-One (many stocks are listed on one exchange)
- **Stock → StockHistory**: One-to-Many (one stock has many historical records)
- **Stock → WatchlistItem**: One-to-Many (one stock can appear in many watchlists)
- **Stock → UserActivity**: One-to-Many (one stock can have many user activities)

### 4.2 User Relationships
- **User → Watchlist**: One-to-Many (one user can have many watchlists)
- **User → UserActivity**: One-to-Many (one user can have many activities)
- **User → SystemConfiguration**: One-to-Many (one user can modify many configurations)

### 4.3 Watchlist Relationships
- **Watchlist → User**: Many-to-One (many watchlists belong to one user)
- **Watchlist → WatchlistItem**: One-to-Many (one watchlist contains many items)

### 4.4 WatchlistItem Relationships
- **WatchlistItem → Watchlist**: Many-to-One (many items belong to one watchlist)
- **WatchlistItem → Stock**: Many-to-One (many watchlist items reference one stock)

### 4.5 Other Relationships
- **Sector → Stock**: One-to-Many (one sector contains many stocks)
- **Exchange → Stock**: One-to-Many (one exchange lists many stocks)
- **StockHistory → Stock**: Many-to-One (many historical records belong to one stock)

## 5. Key Workflows

### 5.1 View Stock List Workflow
1. User navigates to the application homepage
2. System retrieves all active stocks from the database
3. System displays stocks in a paginated list/grid view
4. User can scroll or navigate through pages
5. System loads additional stocks as needed (pagination/infinite scroll)

### 5.2 Search and Filter Stocks Workflow
1. User enters search criteria (ticker symbol, company name, or keywords)
2. User optionally applies filters (sector, exchange, price range)
3. System queries the database with search and filter parameters
4. System returns matching stocks
5. System displays filtered results
6. User can clear filters to return to full list

### 5.3 View Stock Details Workflow
1. User clicks on a stock from the list
2. System retrieves detailed stock information
3. System retrieves recent stock history data
4. System displays comprehensive stock details page
5. For registered users, system shows if stock is in any watchlist
6. System logs the view activity for registered users

### 5.4 Add Stock to Watchlist Workflow (Registered Users)
1. User views a stock detail page
2. User clicks "Add to Watchlist" button
3. System displays user's watchlists
4. User selects target watchlist or creates new one
5. System validates the stock is not already in the watchlist
6. System creates a new WatchlistItem record
7. System confirms successful addition
8. System updates the UI to reflect the change

### 5.5 Manage Watchlist Workflow (Registered Users)
1. User navigates to "My Watchlists" section
2. System retrieves all user's watchlists with stock counts
3. User selects a watchlist to view
4. System displays all stocks in the watchlist
5. User can reorder, add notes, or remove stocks
6. User can rename or delete the watchlist
7. System persists all changes
8. System updates the UI accordingly

### 5.6 Add New Stock Workflow (Admin/Data Manager)
1. Admin/Data Manager navigates to "Add Stock" page
2. User enters stock information in the form
3. System validates all required fields
4. System checks for duplicate ticker symbols
5. User submits the form
6. System validates business rules
7. System creates new Stock record
8. System confirms successful creation
9. System redirects to the new stock's detail page

### 5.7 Update Stock Information Workflow (Admin/Data Manager)
1. Admin/Data Manager navigates to a stock detail page
2. User clicks "Edit" button
3. System displays editable form with current data
4. User modifies stock information
5. System validates changes
6. User submits the form
7. System updates the Stock record
8. System logs the modification with timestamp
9. System confirms successful update

### 5.8 Bulk Import Stocks Workflow (Admin/Data Manager)
1. Admin/Data Manager navigates to "Import Stocks" page
2. User uploads a CSV/Excel file with stock data
3. System validates file format and structure
4. System parses the file and validates each row
5. System displays preview of stocks to be imported
6. System highlights any validation errors
7. User confirms the import
8. System creates Stock records for valid entries
9. System generates import report with success/failure counts
10. System displays the report to the user

### 5.9 User Registration Workflow
1. Guest user clicks "Sign Up" button
2. System displays registration form
3. User enters email, password, and basic information
4. System validates email format and password strength
5. System checks if email already exists
6. User submits the form
7. System creates new User record with "Registered User" role
8. System sends verification email (optional)
9. System logs the user in automatically
10. System redirects to homepage or dashboard

### 5.10 User Authentication Workflow
1. User clicks "Login" button
2. System displays login form
3. User enters email and password
4. System validates credentials
5. System checks user status (active/inactive/suspended)
6. System creates user session
7. System logs the login activity
8. System redirects to intended page or dashboard

## 6. Features & Requirements

### 6.1 Stock Display Module

#### 6.1.1 Stock List View
- **FR-SDL-001**: Display all active stocks in a responsive grid or table layout
- **FR-SDL-002**: Show key information for each stock: ticker symbol, company name, current price, price change (amount and percentage), volume
- **FR-SDL-003**: Support pagination with configurable items per page (25, 50, 100)
- **FR-SDL-004**: Support infinite scroll as an alternative to pagination
- **FR-SDL-005**: Display stock logo/icon when available
- **FR-SDL-006**: Show visual indicators for price movement (green for up, red for down)
- **FR-SDL-007**: Display last updated timestamp for stock data
- **FR-SDL-008**: Support both grid and table view modes with user preference persistence

#### 6.1.2 Stock Detail View
- **FR-SDD-001**: Display comprehensive stock information including all attributes
- **FR-SDD-002**: Show current price prominently with price change indicators
- **FR-SDD-003**: Display company description and basic information
- **FR-SDD-004**: Show sector and industry classification
- **FR-SDD-005**: Display exchange information
- **FR-SDD-006**: Show market capitalization with formatted numbers
- **FR-SDD-007**: Display trading volume
- **FR-SDD-008**: Show 52-week high and low prices
- **FR-SDD-009**: Display company website link (opens in new tab)
- **FR-SDD-010**: Show IPO date and years since IPO
- **FR-SDD-011**: Display historical price chart (line chart for last 30/90/365 days)

### 6.2 Search and Filter Module

#### 6.2.1 Search Functionality
- **FR-SF-001**: Provide a prominent search bar on all pages
- **FR-SF-002**: Support search by ticker symbol (exact and partial match)
- **FR-SF-003**: Support search by company name (partial match, case-insensitive)
- **FR-SF-004**: Display search suggestions as user types (autocomplete)
- **FR-SF-005**: Show "no results" message when search returns empty
- **FR-SF-006**: Highlight search terms in results
- **FR-SF-007**: Support search history for registered users (last 10 searches)
- **FR-SF-008**: Allow clearing search with a single click

#### 6.2.2 Filter Functionality
- **FR-FF-001**: Provide filter panel/sidebar for advanced filtering
- **FR-FF-002**: Filter by sector (multi-select)
- **FR-FF-003**: Filter by exchange (multi-select)
- **FR-FF-004**: Filter by price range (min/max inputs or slider)
- **FR-FF-005**: Filter by market cap range (predefined ranges: small, mid, large cap)
- **FR-FF-006**: Filter by volume range
- **FR-FF-007**: Filter by price change percentage (gainers/losers)
- **FR-FF-008**: Show active filter count badge
- **FR-FF-009**: Allow clearing all filters with one click
- **FR-FF-010**: Persist filter state in URL for sharing
- **FR-FF-011**: Display result count after applying filters

#### 6.2.3 Sorting Functionality
- **FR-SO-001**: Sort by ticker symbol (A-Z, Z-A)
- **FR-SO-002**: Sort by company name (A-Z, Z-A)
- **FR-SO-003**: Sort by current price (low to high, high to low)
- **FR-SO-004**: Sort by price change percentage (biggest gainers/losers)
- **FR-SO-005**: Sort by volume (low to high, high to low)
- **FR-SO-006**: Sort by market cap (low to high, high to low)
- **FR-SO-007**: Display current sort indicator in column headers
- **FR-SO-008**: Persist sort preference for user session

### 6.3 Watchlist Module (Registered Users)

#### 6.3.1 Watchlist Management
- **FR-WM-001**: Allow users to create multiple watchlists
- **FR-WM-002**: Require watchlist name (max 50 characters)
- **FR-WM-003**: Allow optional watchlist description (max 200 characters)
- **FR-WM-004**: Support renaming watchlists
- **FR-WM-005**: Support deleting watchlists with confirmation
- **FR-WM-006**: Automatically create a default "My Watchlist" on first use
- **FR-WM-007**: Display watchlist count and total stocks count
- **FR-WM-008**: Support reordering watchlists
- **FR-WM-009**: Limit maximum watchlists per user to 10

#### 6.3.2 Watchlist Items
- **FR-WI-001**: Add stocks to watchlist from stock detail page
- **FR-WI-002**: Add stocks to watchlist from stock list view (quick add button)
- **FR-WI-003**: Remove stocks from watchlist with confirmation
- **FR-WI-004**: Add optional notes to watchlist items (max 500 characters)
- **FR-WI-005**: Display date when stock was added to watchlist
- **FR-WI-006**: Support reordering stocks within a watchlist (drag-and-drop)
- **FR-WI-007**: Prevent duplicate stocks in the same watchlist
- **FR-WI-008**: Allow moving stocks between watchlists
- **FR-WI-009**: Limit maximum stocks per watchlist to 100
- **FR-WI-010**: Show visual indicator on stock list/detail if stock is in any watchlist

#### 6.3.3 Watchlist Display
- **FR-WD-001**: Display all watchlists in a sidebar or dedicated page
- **FR-WD-002**: Show stock count for each watchlist
- **FR-WD-003**: Display watchlist stocks with same information as main stock list
- **FR-WD-004**: Show aggregate statistics (total value change, top gainer/loser)
- **FR-WD-005**: Support all sorting options within watchlist view
- **FR-WD-006**: Allow quick navigation between watchlists

### 6.4 User Management Module

#### 6.4.1 User Registration
- **FR-UR-001**: Provide registration form with email and password
- **FR-UR-002**: Require first name and last name
- **FR-UR-003**: Validate email format
- **FR-UR-004**: Enforce password strength requirements (min 8 characters, 1 uppercase, 1 number)
- **FR-UR-005**: Check for existing email and show error
- **FR-UR-006**: Send welcome email after registration (optional)
- **FR-UR-007**: Automatically log in user after successful registration
- **FR-UR-008**: Set default role as "Registered User"

#### 6.4.2 User Authentication
- **FR-UA-001**: Provide login form with email and password
- **FR-UA-002**: Validate credentials against database
- **FR-UA-003**: Show appropriate error messages for invalid credentials
- **FR-UA-004**: Create secure session on successful login
- **FR-UA-005**: Implement "Remember Me" functionality (optional)
- **FR-UA-006**: Provide "Forgot Password" functionality
- **FR-UA-007**: Log user out after 24 hours of inactivity
- **FR-UA-008**: Prevent login for suspended or inactive accounts
- **FR-UA-009**: Log all login attempts with timestamp and IP address

#### 6.4.3 User Profile
- **FR-UP-001**: Allow users to view their profile information
- **FR-UP-002**: Allow users to edit first name, last name
- **FR-UP-003**: Allow users to change password (require current password)
- **FR-UP-004**: Allow users to upload profile picture
- **FR-UP-005**: Display registration date and last login date
- **FR-UP-006**: Show user activity statistics (stocks viewed, watchlists created)
- **FR-UP-007**: Allow users to delete their account with confirmation
- **FR-UP-008**: Support user preferences (theme, default view, items per page)

### 6.5 Administration Module

#### 6.5.1 Stock Management (Admin/Data Manager)
- **FR-AM-001**: Provide form to add new stocks with all required fields
- **FR-AM-002**: Validate ticker symbol uniqueness
- **FR-AM-003**: Provide form to edit existing stock information
- **FR-AM-004**: Allow admins to delete stocks (soft delete, mark as inactive)
- **FR-AM-005**: Display audit trail for stock modifications
- **FR-AM-006**: Support bulk import via CSV/Excel file
- **FR-AM-007**: Validate imported data and show error report
- **FR-AM-008**: Allow preview before confirming bulk import
- **FR-AM-009**: Support bulk export of stocks to CSV
- **FR-AM-010**: Provide stock status management (active/inactive)

#### 6.5.2 User Management (Admin Only)
- **FR-AUM-001**: Display list of all users with key information
- **FR-AUM-002**: Support searching users by email or name
- **FR-AUM-003**: Allow viewing user details and activity
- **FR-AUM-004**: Allow changing user roles
- **FR-AUM-005**: Allow suspending/activating user accounts
- **FR-AUM-006**: Allow deleting user accounts with confirmation
- **FR-AUM-007**: Display user statistics (total users, active users, new registrations)
- **FR-AUM-008**: Show user activity logs

#### 6.5.3 System Configuration (Admin Only)
- **FR-AC-001**: Provide interface to manage system settings
- **FR-AC-002**: Configure items per page default
- **FR-AC-003**: Configure session timeout duration
- **FR-AC-004**: Configure maximum watchlists per user
- **FR-AC-005**: Configure maximum stocks per watchlist
- **FR-AC-006**: Manage sector list (add, edit, delete)
- **FR-AC-007**: Manage exchange list (add, edit, delete)
- **FR-AC-008**: Configure data refresh intervals
- **FR-AC-009**: View system logs and error logs

#### 6.5.4 Analytics and Reporting (Admin Only)
- **FR-AR-001**: Display dashboard with key metrics
- **FR-AR-002**: Show total stocks count
- **FR-AR-003**: Show total users count by role
- **FR-AR-004**: Show most viewed stocks (top 10)
- **FR-AR-005**: Show most searched terms
- **FR-AR-006**: Display user activity trends (daily/weekly/monthly)
- **FR-AR-007**: Show watchlist statistics (average stocks per watchlist)
- **FR-AR-008**: Display system health metrics (response time, error rate)
- **FR-AR-009**: Support date range filtering for reports
- **FR-AR-010**: Allow exporting reports to PDF/CSV

### 6.6 Data Management Module

#### 6.6.1 Stock Data Updates
- **FR-DM-001**: Support manual stock price updates by admin/data manager
- **FR-DM-002**: Log all data updates with timestamp and user
- **FR-DM-003**: Display last updated timestamp on stock information
- **FR-DM-004**: Support batch updates for multiple stocks
- **FR-DM-005**: Validate data consistency before saving updates

#### 6.6.2 Historical Data
- **FR-HD-001**: Store daily historical price data for each stock
- **FR-HD-002**: Support importing historical data via CSV
- **FR-HD-003**: Display historical data in chart format
- **FR-HD-004**: Support multiple time ranges (1 month, 3 months, 6 months, 1 year, all time)
- **FR-HD-005**: Calculate and display price change over selected period

### 6.7 UI/UX Module

#### 6.7.1 General UI Requirements
- **FR-UI-001**: Implement responsive design for mobile, tablet, and desktop
- **FR-UI-002**: Provide consistent navigation across all pages
- **FR-UI-003**: Display loading indicators for async operations
- **FR-UI-004**: Show success/error messages for user actions
- **FR-UI-005**: Implement breadcrumb navigation
- **FR-UI-006**: Provide help tooltips for complex features
- **FR-UI-007**: Support keyboard navigation for accessibility
- **FR-UI-008**: Implement dark mode and light mode themes
- **FR-UI-009**: Display user menu with profile and logout options
- **FR-UI-010**: Show application logo and branding consistently

#### 6.7.2 Performance UI
- **FR-PUI-001**: Implement skeleton loaders for content loading
- **FR-PUI-002**: Use lazy loading for images
- **FR-PUI-003**: Implement virtual scrolling for large lists
- **FR-PUI-004**: Cache frequently accessed data in browser
- **FR-PUI-005**: Minimize page reloads with SPA architecture

## 7. Business Rules

### 7.1 Stock Rules
- **BR-ST-001**: Ticker symbols must be unique across the system
- **BR-ST-002**: Ticker symbols must be 1-10 characters, uppercase letters only
- **BR-ST-003**: Stock prices must be positive numbers with up to 2 decimal places
- **BR-ST-004**: Volume must be a non-negative integer
- **BR-ST-005**: Market cap must be a positive number
- **BR-ST-006**: Stock must belong to exactly one sector
- **BR-ST-007**: Stock must be listed on exactly one exchange
- **BR-ST-008**: Opening price, closing price, high, and low must satisfy: low ≤ open ≤ high and low ≤ close ≤ high
- **BR-ST-009**: High price must be greater than or equal to low price
- **BR-ST-010**: Deleted stocks are soft-deleted (marked inactive) not physically removed
- **BR-ST-011**: Company name must be unique
- **BR-ST-012**: IPO date cannot be in the future

### 7.2 User Rules
- **BR-US-001**: Email addresses must be unique across all users
- **BR-US-002**: Email must be in valid format (RFC 5322 compliant)
- **BR-US-003**: Password must be at least 8 characters long
- **BR-US-004**: Password must contain at least one uppercase letter, one lowercase letter, and one number
- **BR-US-005**: Users cannot change their own role
- **BR-US-006**: Only admins can create admin or data manager accounts
- **BR-US-007**: Suspended users cannot log in
- **BR-US-008**: Deleted users cannot be restored (soft delete with anonymization)
- **BR-US-009**: User sessions expire after 24 hours of inactivity
- **BR-US-010**: Users must be 18 years or older (if age is collected)

### 7.3 Watchlist Rules
- **BR-WL-001**: Users can create a maximum of 10 watchlists
- **BR-WL-002**: Each watchlist can contain a maximum of 100 stocks
- **BR-WL-003**: A stock cannot appear twice in the same watchlist
- **BR-WL-004**: Watchlist names must be unique per user
- **BR-WL-005**: Watchlist names must be 1-50 characters
- **BR-WL-006**: Deleting a watchlist deletes all associated watchlist items
- **BR-WL-007**: Anonymous users cannot create watchlists
- **BR-WL-008**: At least one watchlist must exist for a user (default watchlist)
- **BR-WL-009**: Default watchlist cannot be deleted (can be renamed)
- **BR-WL-010**: Deleting a stock removes it from all watchlists

### 7.4 Access Control Rules
- **BR-AC-001**: Anonymous users can only view stock information
- **BR-AC-002**: Registered users can manage their own watchlists only
- **BR-AC-003**: Data managers can add and edit stocks but cannot delete them
- **BR-AC-004**: Only admins can delete stocks and manage users
- **BR-AC-005**: Users can only view and edit their own profile
- **BR-AC-006**: Users cannot view other users' watchlists
- **BR-AC-007**: Admins can view all user data but cannot access user passwords
- **BR-AC-008**: System configuration can only be modified by admins
- **BR-AC-009**: Audit logs cannot be modified or deleted by any user

### 7.5 Data Validation Rules
- **BR-DV-001**: All required fields must be provided before saving
- **BR-DV-002**: Numeric fields must contain valid numbers
- **BR-DV-003**: Date fields must be valid dates
- **BR-DV-004**: URL fields must be valid URLs (if provided)
- **BR-DV-005**: Currency codes must be valid ISO 4217 codes
- **BR-DV-006**: Country codes must be valid ISO 3166-1 alpha-2 codes
- **BR-DV-007**: Text fields must not exceed maximum length limits
- **BR-DV-008**: HTML/script tags are not allowed in text inputs (XSS prevention)
- **BR-DV-009**: File uploads must be of allowed types and within size limits
- **BR-DV-010**: Bulk import files must not exceed 10,000 rows

### 7.6 Business Logic Rules
- **BR-BL-001**: Price change percentage is calculated as: ((current price - previous close) / previous close) × 100
- **BR-BL-002**: Stock status is automatically set to inactive if not updated for 30 days
- **BR-BL-003**: User activity is logged only for registered users
- **BR-BL-004**: Search results are limited to 1000 records maximum
- **BR-BL-005**: Historical data is retained for a minimum of 5 years
- **BR-BL-006**: Stock data timestamps are stored in UTC
- **BR-BL-007**: Display times are converted to user's local timezone
- **BR-BL-008**: Pagination defaults to 25 items per page
- **BR-BL-009**: Autocomplete suggestions are limited to 10 results
- **BR-BL-010**: Failed login attempts are limited to 5 per hour per email

## 8. Non-Functional Requirements

### 8.1 Performance Requirements
- **NFR-PF-001**: Stock list page must load within 2 seconds for up to 10,000 stocks
- **NFR-PF-002**: Stock detail page must load within 1 second
- **NFR-PF-003**: Search results must return within 1 second for any query
- **NFR-PF-004**: API response time must be under 500ms for 95% of requests
- **NFR-PF-005**: System must support 1,000 concurrent users
- **NFR-PF-006**: Database queries must be optimized with appropriate indexes
- **NFR-PF-007**: Images must be optimized and served via CDN
- **NFR-PF-008**: Frontend assets must be minified and compressed
- **NFR-PF-009**: Implement caching strategy for frequently accessed data (cache TTL: 5 minutes for stock data)
- **NFR-PF-010**: Page size must not exceed 2MB including all assets

### 8.2 Security Requirements
- **NFR-SC-001**: All passwords must be hashed using bcrypt with salt (minimum 10 rounds)
- **NFR-SC-002**: Implement HTTPS for all communications
- **NFR-SC-003**: Implement CSRF protection for all state-changing operations
- **NFR-SC-004**: Implement XSS protection by sanitizing all user inputs
- **NFR-SC-005**: Implement SQL injection protection using parameterized queries
- **NFR-SC-006**: Implement rate limiting on API endpoints (100 requests per minute per IP)
- **NFR-SC-007**: Implement session management with secure, httpOnly cookies
- **NFR-SC-008**: Log all authentication attempts and security events
- **NFR-SC-009**: Implement role-based access control (RBAC) for all protected resources
- **NFR-SC-010**: Sensitive data must not be logged or exposed in error messages
- **NFR-SC-011**: Implement Content Security Policy (CSP) headers
- **NFR-SC-012**: Regular security audits and dependency updates
- **NFR-SC-013**: Implement account lockout after 5 failed login attempts (15-minute lockout)
- **NFR-SC-014**: API keys and secrets must be stored in environment variables, not in code

### 8.3 Scalability Requirements
- **NFR-SX-001**: Database must support horizontal scaling
- **NFR-SX-002**: Application must be stateless to support load balancing
- **NFR-SX-003**: System must handle up to 100,000 stocks
- **NFR-SX-004**: System must handle up to 50,000 registered users
- **NFR-SX-005**: Database must support read replicas for read-heavy operations
- **NFR-SX-006**: Implement database connection pooling
- **NFR-SX-007**: Support auto-scaling based on traffic patterns
- **NFR-SX-008**: Implement queue system for background jobs (bulk imports, email sending)

### 8.4 Availability Requirements
- **NFR-AV-001**: System uptime must be 99.5% (excluding planned maintenance)
- **NFR-AV-002**: Planned maintenance windows must be announced 48 hours in advance
- **NFR-AV-003**: System must have automated health checks every 5 minutes
- **NFR-AV-004**: Implement graceful degradation for non-critical features
- **NFR-AV-005**: Database must have automated daily backups with 30-day retention
- **NFR-AV-006**: Implement disaster recovery plan with 24-hour RTO (Recovery Time Objective)
- **NFR-AV-007**: Critical errors must trigger alerts to administrators

### 8.5 Usability Requirements
- **NFR-UX-001**: Application must be accessible (WCAG 2.1 Level AA compliance)
- **NFR-UX-002**: Application must work on modern browsers (Chrome, Firefox, Safari, Edge - last 2 versions)
- **NFR-UX-003**: Mobile responsive design must work on devices with minimum 320px width
- **NFR-UX-004**: All user actions must provide clear feedback within 100ms
- **NFR-UX-005**: Error messages must be user-friendly and actionable
- **NFR-UX-006**: Forms must have inline validation
- **NFR-UX-007**: Application must support keyboard navigation
- **NFR-UX-008**: Color contrast must meet WCAG AA standards (4.5:1 for normal text)
- **NFR-UX-009**: Touch targets must be at least 44×44 pixels on mobile
- **NFR-UX-010**: Application must support screen readers

### 8.6 Maintainability Requirements
- **NFR-MT-001**: Code must follow consistent style guide and formatting
- **NFR-MT-002**: All functions and modules must have clear documentation
- **NFR-MT-003**: Code must have minimum 70% test coverage
- **NFR-MT-004**: Use version control (Git) with clear commit messages
- **NFR-MT-005**: Implement CI/CD pipeline for automated testing and deployment
- **NFR-MT-006**: Database schema changes must use migration scripts
- **NFR-MT-007**: API must be versioned to support backward compatibility
- **NFR-MT-008**: Implement comprehensive logging for debugging
- **NFR-MT-009**: Use environment-specific configuration files
- **NFR-MT-010**: Dependencies must be clearly documented and regularly updated

### 8.7 Compatibility Requirements
- **NFR-CP-001**: Backend must provide RESTful API
- **NFR-CP-002**: API must return JSON responses
- **NFR-CP-003**: Support API documentation using OpenAPI/Swagger
- **NFR-CP-004**: Frontend must be framework-agnostic (or specify framework)
- **NFR-CP-005**: Database must be relational (PostgreSQL, MySQL, or similar)
- **NFR-CP-006**: Support internationalization (i18n) framework for future localization
- **NFR-CP-007**: Date/time handling must support multiple timezones

### 8.8 Compliance Requirements
- **NFR-CL-001**: Comply with GDPR for user data handling (if applicable)
- **NFR-CL-002**: Provide privacy policy and terms of service
- **NFR-CL-003**: Allow users to export their data
- **NFR-CL-004**: Allow users to request account deletion
- **NFR-CL-005**: Implement audit logging for compliance tracking
- **NFR-CL-006**: Retain audit logs for minimum 1 year
- **NFR-CL-007**: Implement data retention policies

### 8.9 Monitoring and Observability
- **NFR-MO-001**: Implement application performance monitoring (APM)
- **NFR-MO-002**: Log all errors with stack traces
- **NFR-MO-003**: Track key business metrics (user registrations, stock views, searches)
- **NFR-MO-004**: Implement real-time alerting for critical errors
- **NFR-MO-005**: Monitor database performance and slow queries
- **NFR-MO-006**: Track API endpoint usage and response times
- **NFR-MO-007**: Implement user analytics (page views, user flows)
- **NFR-MO-008**: Create dashboards for system health monitoring

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**Document Version**: 1.0  
**Last Updated**: 2025-01-XX  
**Author**: Senior Product Manager  
**Status**: Ready for Development