# Technical Specification: [Feature Name]

**Document Status:** Draft | Review | Approved | Implemented
**Version:** 1.0
**Author:** John Doe
**Date:** 2025-01-15
**Reviewers:** Jane Smith, Bob Johnson
**Last Updated:** 2025-01-15

## Executive Summary

Brief 2-3 sentence overview of what this spec covers and why it's being built.

**Problem:** What problem are we solving?
**Solution:** High-level description of the solution
**Impact:** Expected business/user impact

---

## 1. Background

### Context

Provide background on why this feature is needed:
- What's the current situation?
- What pain points exist?
- What's driving this change?

### Goals

- **Primary Goal:** Main objective of this feature
- **Secondary Goals:** Additional benefits
- **Success Metrics:** How we'll measure success
  - Metric 1: [Description] - Target: [Value]
  - Metric 2: [Description] - Target: [Value]

### Non-Goals

What this specification explicitly does NOT cover:
- Non-goal 1
- Non-goal 2
- Future considerations (out of scope for v1)

---

## 2. Requirements

### Functional Requirements

#### FR-1: User Authentication
**Priority:** P0 (Must Have)
**Description:** Users must be able to authenticate using email/password

**Acceptance Criteria:**
- [ ] User can register with email and password
- [ ] User can log in with credentials
- [ ] User receives email verification
- [ ] User can reset forgotten password
- [ ] Session expires after 7 days of inactivity

**Dependencies:** None

#### FR-2: Social Login
**Priority:** P1 (Should Have)
**Description:** Users can authenticate using OAuth providers

**Acceptance Criteria:**
- [ ] Support Google OAuth
- [ ] Support GitHub OAuth
- [ ] Link social accounts to existing accounts
- [ ] Unlink social accounts

**Dependencies:** FR-1

#### FR-3: Two-Factor Authentication
**Priority:** P2 (Nice to Have)
**Description:** Optional 2FA for enhanced security

**Acceptance Criteria:**
- [ ] Enable/disable 2FA in settings
- [ ] Support TOTP (Google Authenticator, Authy)
- [ ] Backup codes generation
- [ ] Recovery process if device is lost

**Dependencies:** FR-1

### Non-Functional Requirements

#### Performance
- **Response Time:** API endpoints < 200ms p95
- **Throughput:** Support 1000 requests/second
- **Database Queries:** < 50ms p95
- **Page Load:** First contentful paint < 1.5s

#### Scalability
- **Concurrent Users:** Support 100,000 simultaneous users
- **Data Growth:** Handle 10M user records
- **Horizontal Scaling:** Support 10 application instances

#### Security
- **Authentication:** JWT-based with refresh tokens
- **Password Hashing:** bcrypt with 12 rounds
- **Rate Limiting:** 100 requests/hour per IP
- **Data Encryption:** AES-256 at rest, TLS 1.3 in transit

#### Availability
- **Uptime:** 99.9% SLA
- **Recovery Time:** RTO < 4 hours, RPO < 1 hour
- **Backup:** Daily automated backups, 30-day retention

#### Compliance
- GDPR compliant (data export/deletion)
- SOC 2 Type II requirements
- PCI DSS (if handling payments)

---

## 3. System Architecture

### High-Level Architecture

### Component Diagram

#### Frontend (React)
- **Login Page:** Email/password and social login
- **Registration Page:** User signup with validation
- **Settings Page:** Manage 2FA and connected accounts
- **Components:** Reusable auth components

#### Backend (Node.js/Express)
- **Auth Controller:** Handle authentication requests
- **User Controller:** Manage user data
- **Auth Middleware:** Validate JWT tokens
- **Rate Limiter:** Prevent abuse

#### Database (PostgreSQL)
- **users table:** User account data
- **sessions table:** Active sessions
- **oauth_connections table:** Social login links

#### Cache (Redis)
- Session storage
- Rate limit counters
- Temporary tokens (password reset, email verification)

---

## 4. Data Model

### Database Schema

```sql
-- Users table
CREATE TABLE users (
  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
  email VARCHAR(255) UNIQUE NOT NULL,
  password_hash VARCHAR(255),
  email_verified BOOLEAN DEFAULT FALSE,
  two_factor_enabled BOOLEAN DEFAULT FALSE,
  two_factor_secret VARCHAR(32),
  created_at TIMESTAMP DEFAULT NOW(),
  updated_at TIMESTAMP DEFAULT NOW(),
  last_login_at TIMESTAMP
);

-- OAuth connections
CREATE TABLE oauth_connections (
  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
  user_id UUID REFERENCES users(id) ON DELETE CASCADE,
  provider VARCHAR(50) NOT NULL, -- 'google', 'github'
  provider_user_id VARCHAR(255) NOT NULL,
  access_token TEXT,
  refresh_token TEXT,
  created_at TIMESTAMP DEFAULT NOW(),
  UNIQUE(provider, provider_user_id)
);

-- Sessions
CREATE TABLE sessions (
  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
  user_id UUID REFERENCES users(id) ON DELETE CASCADE,
  token VARCHAR(255) UNIQUE NOT NULL,
  expires_at TIMESTAMP NOT NULL,
  created_at TIMESTAMP DEFAULT NOW(),
  ip_address INET,
  user_agent TEXT
);

-- Indexes
CREATE INDEX idx_users_email ON users(email);
CREATE INDEX idx_sessions_token ON sessions(token);
CREATE INDEX idx_sessions_user_id ON sessions(user_id);
CREATE INDEX idx_oauth_user_id ON oauth_connections(user_id);

interface User {
  id: string;
  email: string;
  emailVerified: boolean;
  twoFactorEnabled: boolean;
  createdAt: string;
  updatedAt: string;
  lastLoginAt?: string;
}

interface LoginRequest {
  email: string;
  password: string;
  twoFactorCode?: string;
}

interface LoginResponse {
  success: boolean;
  token: string;
  refreshToken: string;
  user: User;
  expiresIn: number;
}

interface RegisterRequest {
  email: string;
  password: string;
  confirmPassword: string;
}

{
  "email": "user@example.com",
  "password": "SecurePass123!",
  "confirmPassword": "SecurePass123!"
}

{
  "success": true,
  "user": {
    "id": "550e8400-e29b-41d4-a716-446655440000",
    "email": "user@example.com",
    "emailVerified": false
  },
  "message": "Verification email sent"
}

{
  "email": "user@example.com",
  "password": "SecurePass123!",
  "twoFactorCode": "123456"
}

{
  "success": true,
  "token": "eyJhbGciOiJIUzI1NiIs...",
  "refreshToken": "eyJhbGciOiJIUzI1NiIs...",
  "user": {
    "id": "550e8400-e29b-41d4-a716-446655440000",
    "email": "user@example.com"
  },
  "expiresIn": 3600
}

// Log structure
{
  "timestamp": "2025-01-15T14:30:00Z",
  "level": "info",
  "event": "user_login",
  "userId": "550e8400-...",
  "ip": "192.168.1.1",
  "userAgent": "Mozilla/5.0...",
  "success": true,
  "duration": 125
}

## Best Practices

### ✅ DO
- Include acceptance criteria for each requirement
- Provide architecture diagrams
- Document API contracts
- Specify performance requirements
- List risks and mitigations
- Include implementation timeline
- Add success metrics
- Document security considerations
- Version your specs
- Get stakeholder review

### ❌ DON'T
- Be vague about requirements
- Skip non-functional requirements
- Forget about security
- Ignore alternatives
- Skip testing strategy
- Forget monitoring/observability
- Leave questions unanswered

## Resources

- [Google Design Docs](https://www.industrialempathy.com/posts/design-docs-at-google/)
- [RFC Template](https://github.com/philips/template-rfcs)
- [Architecture Decision Records](https://adr.github.io/)
- [Amazon Press Release / FAQ](https://www.productplan.com/glossary/working-backward-amazon-method/)