514 lines
13 KiB
Markdown
514 lines
13 KiB
Markdown
<!--META
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{
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"kind": "design_document",
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"tokens": ["FeatureId", "CreatedDate", "Title"]
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}
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-->
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# Design Document: {Title}
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**Feature ID:** {FeatureId}
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**Status:** Draft
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**Created:** {CreatedDate}
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**Last Updated:** {CreatedDate}
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**Authors:** [To be filled by AI from discussion participants]
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**Reviewers:** [To be filled from discussion]
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---
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## Executive Summary
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[1-2 paragraph overview of the feature and this design's approach. What problem does this solve? What's the proposed solution at a high level?]
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---
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## 1. Context & Problem Statement
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### Background
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[What is the current state? What pain points or opportunities led to this feature request?]
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### Business Goals
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- [Goal 1: e.g., Reduce user onboarding time by 50%]
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- [Goal 2: e.g., Support 10,000 concurrent users]
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- [Goal 3: e.g., Enable third-party integrations]
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### Success Metrics
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| Metric | Target | Measurement Method |
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|--------|--------|-------------------|
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| [e.g., Page load time] | [< 2s] | [Performance testing] |
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| [e.g., User satisfaction] | [> 4.5/5] | [Post-feature survey] |
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---
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## 2. Requirements
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### Functional Requirements
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**Must Have (MVP):**
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- [ ] [FR-1: User can create account with email/password]
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- [ ] [FR-2: User can reset password via email]
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- [ ] [FR-3: User can log in with Google OAuth]
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**Should Have (Nice to Have):**
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- [ ] [FR-4: Remember me functionality]
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- [ ] [FR-5: Two-factor authentication]
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**Won't Have (Out of Scope):**
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- [FR-6: Social login with Facebook/Twitter (deferred to v2)]
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- [FR-7: Biometric authentication (platform limitations)]
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### Non-Functional Requirements
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**Performance:**
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- Response time: < 200ms for API calls
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- Throughput: Support 1,000 requests/second
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- Database queries: < 50ms p95
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**Security:**
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- Password hashing: bcrypt with salt
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- Token expiration: 1 hour for access, 7 days for refresh
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- Rate limiting: 10 failed login attempts = 15min lockout
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**Scalability:**
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- Horizontal scaling: Support 10+ app instances
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- Database: Read replicas for query performance
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- Caching: Redis for session storage
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**Reliability:**
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- Uptime: 99.9% SLA
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- Data durability: Daily backups with 30-day retention
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- Graceful degradation: Fallback to email-only if OAuth fails
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---
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## 3. Options Considered
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### Option 1: [Name, e.g., "In-house Authentication System"]
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**Approach:**
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[Description of this option]
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**Pros:**
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- ✅ [Pro 1]
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- ✅ [Pro 2]
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**Cons:**
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- ❌ [Con 1]
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- ❌ [Con 2]
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**Cost/Complexity:**
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- Development: [X person-weeks]
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- Maintenance: [Y hours/month]
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- Infrastructure: [Z $/month]
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**Risk Assessment:**
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- [Risk 1: Security vulnerabilities - HIGH]
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- [Risk 2: Development timeline - MEDIUM]
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---
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### Option 2: [Name, e.g., "Third-Party Auth Service (Auth0)"]
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**Approach:**
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[Description]
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**Pros:**
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- ✅ [Pro 1]
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- ✅ [Pro 2]
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**Cons:**
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- ❌ [Con 1]
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- ❌ [Con 2]
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**Cost/Complexity:**
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- Development: [X person-weeks]
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- Maintenance: [Y hours/month]
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- Infrastructure: [Z $/month]
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**Risk Assessment:**
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- [Risk 1]
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- [Risk 2]
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---
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### Option 3: [Name, if applicable]
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[Repeat structure from Option 1/2]
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---
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## 4. Decision & Rationale
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### Selected Approach: [Option Name]
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**Primary Reasons:**
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1. [Reason 1: Aligns with technical stack]
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2. [Reason 2: Lowest total cost of ownership]
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3. [Reason 3: Fastest time to market]
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**Trade-offs Accepted:**
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- [Trade-off 1: Higher infrastructure costs vs. lower dev time]
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- [Trade-off 2: Vendor lock-in vs. managed service reliability]
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**Alternatives Rejected:**
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- **Option X** rejected because: [reason]
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- **Option Y** rejected because: [reason]
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**Key Assumptions:**
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- [Assumption 1: User growth will remain under 100K for next 12 months]
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- [Assumption 2: OAuth providers maintain 99.9% uptime]
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**When to Revisit:**
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- If user base exceeds 500K (cost model changes)
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- If OAuth vendor has >2 major outages in 6 months
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- After 1 year in production (reevaluate build vs. buy)
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---
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## 5. Architecture
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### System Architecture Diagram
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```
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[Insert diagram here - can be ASCII art, PlantUML, or image link]
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Example:
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┌─────────────┐ ┌──────────────┐ ┌─────────────┐
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│ Browser │─────▶│ API Gateway │─────▶│ Auth │
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│ │◀─────│ │◀─────│ Service │
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└─────────────┘ └──────────────┘ └─────────────┘
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│ │
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│ ▼
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│ ┌──────────────┐
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│ │ User DB │
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│ │ (Postgres) │
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│ └──────────────┘
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▼
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┌──────────────┐
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│ Session │
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│ Store │
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│ (Redis) │
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└──────────────┘
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```
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### Component Breakdown
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**Component 1: [Name, e.g., "Authentication Service"]**
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- **Responsibility:** Handle user login, registration, token issuance
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- **Technology:** Node.js (Express), PassportJS
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- **Interfaces:**
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- REST API: `/auth/login`, `/auth/register`, `/auth/refresh`
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- Events: `user.logged_in`, `user.registered`
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- **Dependencies:** User DB, Session Store, Email Service
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**Component 2: [Name]**
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[Repeat structure]
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### Data Models
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**User Table:**
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```sql
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CREATE TABLE users (
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id UUID PRIMARY KEY,
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email VARCHAR(255) UNIQUE NOT NULL,
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password_hash VARCHAR(255),
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oauth_provider VARCHAR(50),
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oauth_id VARCHAR(255),
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created_at TIMESTAMP DEFAULT NOW(),
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updated_at TIMESTAMP DEFAULT NOW(),
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INDEX idx_email (email),
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UNIQUE idx_oauth (oauth_provider, oauth_id)
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);
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```
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**Session Table:**
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```sql
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CREATE TABLE sessions (
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id UUID PRIMARY KEY,
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user_id UUID REFERENCES users(id),
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access_token VARCHAR(500) NOT NULL,
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refresh_token VARCHAR(500),
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expires_at TIMESTAMP NOT NULL,
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created_at TIMESTAMP DEFAULT NOW()
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);
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```
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### API Contracts
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**POST /auth/register**
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```json
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Request:
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{
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"email": "user@example.com",
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"password": "SecurePass123!",
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"name": "John Doe"
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}
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Response (201 Created):
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{
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"user_id": "uuid",
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"access_token": "jwt",
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"refresh_token": "jwt",
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"expires_in": 3600
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}
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Errors:
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400 - Invalid email format
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409 - Email already registered
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422 - Password too weak
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```
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**POST /auth/login**
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[Similar structure]
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---
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## 6. Implementation Plan
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### Phases
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**Phase 1: Core Authentication (Week 1-2)**
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- [ ] Set up database schema
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- [ ] Implement email/password registration
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- [ ] Implement login endpoint
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- [ ] Add password hashing (bcrypt)
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- [ ] Write unit tests
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**Phase 2: OAuth Integration (Week 3)**
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- [ ] Integrate Google OAuth
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- [ ] Add OAuth callback handling
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- [ ] Link OAuth accounts to existing users
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- [ ] Test OAuth flow
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**Phase 3: Security Hardening (Week 4)**
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- [ ] Add rate limiting
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- [ ] Implement token refresh
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- [ ] Add password reset flow
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- [ ] Security audit
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**Phase 4: Testing & Deployment (Week 5)**
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- [ ] End-to-end testing
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- [ ] Load testing
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- [ ] Documentation
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- [ ] Production deployment
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### Dependencies
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- **External:**
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- Google OAuth credentials (waiting on: Platform team)
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- Email service API key (waiting on: DevOps)
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- **Internal:**
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- User profile service (blocks: User settings feature)
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- Session management (required by: All authenticated endpoints)
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### Resource Requirements
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- **Development:** 1 backend engineer (full-time, 5 weeks)
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- **Design:** 0.5 designer (mockups, 1 week)
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- **QA:** 0.5 QA engineer (testing, 1 week)
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- **Infrastructure:** $200/month (database + Redis)
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---
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## 7. Risks & Mitigations
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| Risk | Probability | Impact | Mitigation |
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|------|-------------|--------|------------|
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| OAuth provider downtime | Medium | High | Fallback to email auth; cache OAuth tokens |
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| Password breach | Low | Critical | Bcrypt + salt; enforce strong passwords; rate limit |
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| Database bottleneck | Medium | High | Add read replicas; implement caching |
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| Token theft | Medium | High | Short expiration; secure httpOnly cookies |
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### Security Considerations
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**Threat Model:**
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- **Threat 1: Brute force attacks** → Mitigation: Rate limiting, CAPTCHA after 3 failures
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- **Threat 2: SQL injection** → Mitigation: Parameterized queries, ORM usage
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- **Threat 3: XSS in user data** → Mitigation: Input validation, output encoding
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**Compliance:**
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- GDPR: User data deletion within 30 days of request
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- CCPA: User data export API endpoint
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- SOC 2: Audit logging for all auth events
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---
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## 8. Testing Strategy
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### Unit Tests
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- Password hashing/validation
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- Token generation/validation
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- Input validation logic
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- Coverage target: 90%
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### Integration Tests
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- Registration flow (email + OAuth)
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- Login flow (email + OAuth)
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- Token refresh flow
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- Password reset flow
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### End-to-End Tests
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- New user signup journey
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- Returning user login journey
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- OAuth account linking
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- Session expiration handling
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### Performance Tests
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- Concurrent logins: 1,000 users/second
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- Database query performance: < 50ms p95
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- API response time: < 200ms p95
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---
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## 9. Monitoring & Observability
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### Metrics to Track
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**Business Metrics:**
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- Daily active users (DAU)
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- Registration conversion rate
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- OAuth vs. email signup ratio
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**Technical Metrics:**
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- API response time (p50, p95, p99)
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- Error rate by endpoint
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- Database connection pool utilization
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- Cache hit rate
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### Alerts
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- Error rate > 5% for 5 minutes → Page on-call engineer
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- Response time p95 > 500ms → Slack warning
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- Failed login attempts > 100/min → Slack + investigate
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### Dashboards
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- Real-time: Login success/failure rates, active sessions
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- Daily: User growth, OAuth provider breakdown
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- Weekly: Performance trends, error analysis
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---
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## 10. Documentation & Training
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### User-Facing Documentation
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- [ ] Registration guide
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- [ ] Password reset guide
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- [ ] OAuth connection guide
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- [ ] Security best practices
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### Developer Documentation
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- [ ] API reference (OpenAPI spec)
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- [ ] Local development setup
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- [ ] Testing guide
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- [ ] Deployment runbook
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### Training Materials
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- [ ] Team demo of authentication flow
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- [ ] Security review session
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- [ ] Runbook walkthrough for on-call engineers
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---
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## 11. Rollout Plan
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### Feature Flags
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```yaml
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feature_flags:
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auth_email_registration: true
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auth_google_oauth: false # Enable after testing
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auth_password_reset: false # Enable in phase 2
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```
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### Rollout Stages
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1. **Internal Alpha (Week 1)**
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- Deploy to staging
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- Team testing (10 users)
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- Fix critical bugs
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2. **Beta (Week 2)**
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- Deploy to 10% of production traffic
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- Monitor error rates
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- Collect user feedback
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3. **General Availability (Week 3)**
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- Ramp to 50%, then 100%
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- Enable OAuth
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- Sunset old authentication system (Week 4)
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### Rollback Plan
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- **Trigger:** Error rate > 10% or critical security issue
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- **Procedure:**
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1. Disable feature flag
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2. Route traffic to old system
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3. Incident post-mortem within 24 hours
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- **RTO:** 5 minutes (time to disable flag)
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- **RPO:** 0 (no data loss)
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---
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## 12. Future Enhancements
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### Deferred to v2
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- Two-factor authentication (SMS, TOTP)
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- Social login (Facebook, Twitter, GitHub)
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- Biometric authentication
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- SSO for enterprise customers
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### Technical Debt Accepted
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- [Debt 1: Monolithic auth service - plan to split into microservices after 100K users]
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- [Debt 2: In-memory session cache - migrate to distributed cache under high load]
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---
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## 13. Acceptance Criteria
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This design is considered complete and ready for implementation when:
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- [x] All stakeholders have reviewed and approved
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- [ ] Security team has completed threat model review
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- [ ] At least 2 technical reviewers have signed off
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- [ ] All "Must Have" functional requirements are addressed
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- [ ] Performance targets are achievable (validated by load test plan)
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- [ ] Rollback plan is documented and tested
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- [ ] Cost estimate approved by finance
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---
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## 14. Appendices
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### Appendix A: Research & References
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- [Link to competitive analysis]
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- [Link to user research findings]
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- [Link to technology evaluation matrix]
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### Appendix B: Meeting Notes
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**Design Review 1 (YYYY-MM-DD):**
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- Attendees: [Names]
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- Decisions: [Key decisions]
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- Action items: [Follow-ups]
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### Appendix C: Change Log
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| Date | Author | Change |
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|------|--------|--------|
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| {CreatedDate} | AI_Claude | Initial draft from feature discussion |
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---
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**Document Status:** 🟡 Draft - Awaiting Review
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**Next Review Date:** [YYYY-MM-DD]
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**Related Documents:**
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- Feature Discussion: `../discussions/design.discussion.md`
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- Implementation Plan: `../implementation/plan.md` (created after approval)
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