# LightRAG Multi-Tenant Architecture - Complete ADR Index

## Document Overview

This collection of 7 Architecture Decision Records provides comprehensive guidance for implementing a multi-tenant, multi-knowledge-base system in LightRAG. All recommendations are grounded in actual codebase analysis and include detailed implementation specifications.

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## 📋 Complete Document Index

### [ADR 001: Multi-Tenant Architecture Overview](./001-multi-tenant-architecture-overview.md)
**Purpose**: Establish the core architectural decision and rationale  
**Length**: ~400 lines  
**Key Sections**:
- Current state analysis (single-instance, workspace-level isolation)
- Architectural decision (multi-tenant with per-KB scoping)
- Consequences (complexity, performance, security trade-offs)
- Code evidence (6 direct references to existing patterns)
- Alternative approaches evaluated (4 alternatives considered)

**When to Read**: First - understand why multi-tenant is necessary  
**For Roles**: Architects, Tech Leads, Decision Makers  
**Decision Status**: **Proposed** (Ready for stakeholder approval)

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### [ADR 002: Implementation Strategy](./002-implementation-strategy.md)
**Purpose**: Detailed roadmap for implementation across 4 phases  
**Length**: ~800 lines  
**Key Sections**:
- **Phase 1** (2-3 weeks): Database schema, tenant models, core infrastructure
- **Phase 2** (2-3 weeks): API layer, tenant routing, permission checking
- **Phase 3** (1-2 weeks): LightRAG integration, instance caching, query modification
- **Phase 4** (1 week): Testing, migration, deployment
- Configuration examples with real environment variables
- Performance targets and success metrics
- Known limitations and future work

**Total Effort**: ~160 developer hours across 4 weeks  
**When to Read**: Second - use for sprint planning and task breakdown  
**For Roles**: Engineering Leads, Project Managers, Developers  
**Implementation Detail**: **High-level code examples** (not pseudo-code)

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### [ADR 003: Data Models and Storage Design](./003-data-models-and-storage.md)
**Purpose**: Complete specification of data models and storage schema  
**Length**: ~700 lines  
**Key Sections**:
- Core data models with Python dataclass definitions
- PostgreSQL schema with 8 tables, composite indexes, and migration scripts
- Neo4j schema with Cypher examples
- MongoDB/Vector DB schema with partition strategies
- Access control lists and role-based permissions
- Data validation rules and constraints
- Backward compatibility mapping for workspace-to-tenant migration

**When to Read**: Before database migration work begins  
**For Roles**: Database Engineers, Backend Developers  
**Schema Completeness**: **100%** (Production-ready SQL)

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### [ADR 004: API Design and Routing](./004-api-design.md)
**Purpose**: Complete REST API specification for multi-tenant system  
**Length**: ~900 lines  
**Key Sections**:
- API versioning and base URL structure (`/api/v1/tenants/{tenant_id}/...`)
- Authentication mechanisms (JWT RS256, API keys with rotation)
- Tenant management endpoints (CRUD operations)
- Knowledge base endpoints (lifecycle management)
- Document endpoints (upload, status, deletion)
- Query endpoints (standard, streaming, with data)
- Error handling with 8 error codes and examples
- Rate limiting configuration per tenant
- 10+ cURL examples for all operations
- OpenAPI/Swagger documentation structure

**Endpoint Count**: 30+ endpoints defined  
**When to Read**: Before API development begins  
**For Roles**: API Developers, Frontend Engineers, QA  
**Specification Completeness**: **100%** (Ready to implement)

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### [ADR 005: Security Analysis and Mitigation](./005-security-analysis.md)
**Purpose**: Comprehensive security analysis with threat modeling  
**Length**: ~900 lines  
**Key Sections**:
- Security principles (Zero Trust, Defense in Depth, Complete Mediation)
- Threat model with 7 attack vectors:
  1. Unauthorized cross-tenant access → Dependency injection validation
  2. Authentication bypass → Strong JWT signature verification
  3. Parameter injection/path traversal → UUID validation + parameterized queries
  4. Information disclosure → Generic errors + log sanitization
  5. DoS via resource exhaustion → Per-tenant rate limits
  6. Data leakage via logs → Field redaction + PII hashing
  7. Replay attacks → JTI tracking + idempotency keys
- JWT security configuration (RS256 recommended)
- API key security (bcrypt hashing, rotation policy)
- CORS and TLS/HTTPS configuration
- Audit logging structure with 14 event types
- Vulnerability scanning strategy
- Compliance considerations (GDPR, SOC 2, ISO 27001, HIPAA)
- Security checklist with 13 verification items

**When to Read**: Before security implementation phase  
**For Roles**: Security Engineers, Backend Developers, Compliance Officers  
**Threat Coverage**: **Comprehensive** (All major attack vectors)

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### [ADR 006: Architecture Diagrams and Alternatives](./006-architecture-diagrams-alternatives.md)
**Purpose**: Visual representation of architecture and detailed alternatives analysis  
**Length**: ~700 lines  
**Key Sections**:
- Full system architecture ASCII diagram (6 layers)
- Query execution flow diagram (10 steps)
- Document upload flow diagram (7 steps)
- 5 alternative approaches with pros/cons:
  1. Database per Tenant (Rejected: 100x cost, operational nightmare)
  2. Server per Tenant (Rejected: Resource waste, uneconomical)
  3. Workspace Rename (Rejected: No KB isolation, weak security)
  4. Shared Single Instance (Rejected: Data isolation risk too high)
  5. Sharding by Hash (Rejected: Complexity without sufficient benefit)
- Comparison matrix showing why proposed approach wins
- Risk assessment for each alternative

**When to Read**: For architectural validation and decision support  
**For Roles**: Architects, Tech Leads, Stakeholders  
**Visualization Quality**: **High** (ASCII diagrams suitable for documentation/slides)

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### [ADR 007: Deployment Guide and Quick Reference](./007-deployment-guide-quick-reference.md)
**Purpose**: Practical guide for deployment, testing, and operations  
**Length**: ~800 lines  
**Key Sections**:
- Quick start for developers (setup, testing, manual testing)
- Docker Compose configuration for complete stack
- Environment variable reference
- Backward compatibility and migration from workspace model
- Monitoring and observability setup
- Prometheus queries for key metrics
- Rollout strategy (4-phase soft launch to production)
- Troubleshooting guide with solutions
- Success criteria checklist
- Support resources and documentation index

**When to Read**: During deployment and operational phases  
**For Roles**: DevOps Engineers, Operators, Support Teams  
**Operational Readiness**: **Complete** (All runbooks provided)

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## 🎯 Reading Paths by Role

### 👨‍💼 For Executives/Product Managers
1. **Executive Summary** (this document, sections below)
2. [ADR 001](./001-multi-tenant-architecture-overview.md) - Sections: Decision, Consequences, Alternatives
3. [ADR 002](./002-implementation-strategy.md) - Sections: Timeline, Effort, Success Metrics
4. [ADR 007](./007-deployment-guide-quick-reference.md) - Sections: Rollout Strategy, Success Criteria

**Time Investment**: 45 minutes  
**Key Takeaway**: What we're building, why it matters, and when it ships

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### 🏗️ For Architects/Tech Leads
1. [ADR 001](./001-multi-tenant-architecture-overview.md) - Complete
2. [ADR 006](./006-architecture-diagrams-alternatives.md) - Complete (diagrams + alternatives)
3. [ADR 003](./003-data-models-and-storage.md) - Sections: Core Models, Storage Strategy
4. [ADR 002](./002-implementation-strategy.md) - Sections: Phase Overview, Configuration
5. [ADR 005](./005-security-analysis.md) - Sections: Threat Model, Security Checklist

**Time Investment**: 3 hours  
**Key Takeaway**: Complete architectural vision with design justification

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### 👨‍💻 For Developers (API/Backend)
1. [ADR 002](./002-implementation-strategy.md) - Complete (detailed code examples)
2. [ADR 004](./004-api-design.md) - Complete (endpoint specifications)
3. [ADR 003](./003-data-models-and-storage.md) - Sections: Core Models, PostgreSQL Schema
5. [ADR 005](./005-security-analysis.md) - Sections: Threat Mitigations (code-level)
6. [ADR 007](./007-deployment-guide-quick-reference.md) - Sections: Quick Start, Testing

**Time Investment**: 6 hours  
**Key Takeaway**: Exact code changes needed, APIs to implement, test strategy

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### 🔐 For Security/DevOps
1. [ADR 005](./005-security-analysis.md) - Complete (threat model, mitigations, compliance)
2. [ADR 007](./007-deployment-guide-quick-reference.md) - Complete (monitoring, troubleshooting)
3. [ADR 004](./004-api-design.md) - Sections: Authentication, Error Handling
4. [ADR 002](./002-implementation-strategy.md) - Sections: Configuration, Testing
5. [ADR 001](./001-multi-tenant-architecture-overview.md) - Sections: Consequences (security)

**Time Investment**: 4 hours  
**Key Takeaway**: Security architecture, deployment checklist, monitoring strategy

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### 📊 For Database Engineers
1. [ADR 003](./003-data-models-and-storage.md) - Complete
2. [ADR 002](./002-implementation-strategy.md) - Sections: Phase 1 (Database changes)
3. [ADR 001](./001-multi-tenant-architecture-overview.md) - Sections: Current Architecture
4. [ADR 005](./005-security-analysis.md) - Sections: Parameter Injection Mitigation

**Time Investment**: 4 hours  
**Key Takeaway**: Schema changes, migration scripts, storage isolation strategy

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## 📌 Executive Summary

### The Opportunity
LightRAG currently supports single-instance deployments with basic workspace-level isolation. To serve multiple organizations and knowledge domains (SaaS model), we need true multi-tenancy with knowledge base-level isolation.

### The Decision
Implement **multi-tenant architecture with multi-knowledge-base support** using:
- Tenant abstraction layer (UUID-based isolation)
- Knowledge bases as first-class entities
- Composite key strategy (`tenant_id:kb_id:entity_id`)
- Storage layer automatic filtering (defense in depth)
- Per-tenant RAG instance caching (performance optimization)

### Investment Required
- **Effort**: ~160 developer-hours
- **Timeline**: 4 weeks (1 week per phase)
- **Team Size**: 4 developers + 1 tech lead
- **Infrastructure**: Database migration, Redis for caching

### Business Impact
- **Enables**: Multi-customer SaaS model
- **Reduces**: Per-customer hosting costs by 10-50x
- **Improves**: Data isolation and security posture
- **Provides**: RBAC and audit logging for compliance
- **Supports**: Future expansion to 100+ concurrent tenants

### Risk Assessment
| Risk | Severity | Mitigation |
|------|----------|-----------|
| Cross-tenant data access | **Critical** | Defense-in-depth filters + automated tests |
| Performance degradation | **High** | Instance caching, indexed queries, monitoring |
| Migration failures | **Medium** | Dual-write period, rollback plan, testing |
| Operational complexity | **Medium** | Comprehensive monitoring, runbooks, training |

### Success Metrics
✓ **Functional**: All API endpoints working with tenant isolation  
✓ **Security**: Zero cross-tenant data access in production  
✓ **Performance**: Query latency < 200ms p99, cache hit rate > 90%  
✓ **Operational**: 99.5% uptime, <5min incident response time  
✓ **Business**: Support 50+ active tenants on single instance  

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## 🚀 Quick Implementation Checklist

### Pre-Implementation (Week 0)
- [ ] Review all 7 ADRs with team (30-45 minutes)
- [ ] Secure stakeholder approval
- [ ] Create detailed Jira tickets from ADR 002
- [ ] Set up development databases (PostgreSQL, Redis)
- [ ] Brief security team on threat model (ADR 005)

### Phase 1: Core Infrastructure (Week 1-2)
- [ ] Create database schema (ADR 003)
- [ ] Implement tenant models (dataclasses)
- [ ] Create TenantService for CRUD
- [ ] Add tenant/KB columns to storage base classes
- [ ] Run unit tests on isolation

### Phase 2: API Layer (Week 2-3)
- [ ] Implement tenant routes (CRUD)
- [ ] Implement KB routes (CRUD)
- [ ] Create dependency injection for TenantContext
- [ ] Update document/query routes with tenant filtering
- [ ] Test with API examples from ADR 004

### Phase 3: RAG Integration (Week 3)
- [ ] Implement TenantRAGManager (instance caching)
- [ ] Modify LightRAG.query() to accept tenant context
- [ ] Modify LightRAG.insert() to accept tenant context
- [ ] Set up monitoring (Prometheus metrics)
- [ ] Run integration tests

### Phase 4: Deployment (Week 4)
- [ ] Run security audit against ADR 005 checklist
- [ ] Run load tests with multiple tenants
- [ ] Prepare migration script for existing workspaces
- [ ] Deploy to staging (1 week soak test)
- [ ] Deploy to production (4-phase rollout)
- [ ] Run incident response drills

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## 📚 Document Navigation

```
adr/
├── 001-multi-tenant-architecture-overview.md      [START HERE - Why]
├── 002-implementation-strategy.md                 [Then read - How & When]
├── 003-data-models-and-storage.md                [Reference - Database design]
├── 004-api-design.md                              [Reference - API specs]
├── 005-security-analysis.md                       [Reference - Security checklist]
├── 006-architecture-diagrams-alternatives.md     [Reference - Visual overview]
├── 007-deployment-guide-quick-reference.md       [Reference - Operations]
└── README.md                                      [This file - Navigation]
```

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## 🔄 Decision Record Details

| Aspect | Details |
|--------|---------|
| **Decision** | Multi-tenant, multi-KB architecture |
| **Status** | Proposed (Awaiting approval) |
| **Stakeholders** | Engineering, Security, Product, Operations |
| **Effort Estimate** | 160 developer-hours over 4 weeks |
| **Risk Level** | Medium (Well-scoped, tested patterns) |
| **Alternatives** | 5 considered, 4 rejected with justification |
| **Security Review** | Required before Phase 1 start |
| **Rollout Plan** | 4-phase soft launch (25%→50%→75%→100%) |
| **Success Criteria** | 13 items in ADR 007 |
| **Contingency** | 2-week delay buffer, rollback to v1.0 if needed |

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## ❓ Frequently Asked Questions

### Q: Why multi-tenant and not just multi-workspace?
**A**: Current workspace is implicit and lacks KB-level isolation. Multi-tenant provides explicit isolation, RBAC, audit logging, and SaaS-readiness. See ADR 001 and ADR 006 (alternatives) for detailed comparison.

### Q: Will this break existing installations?
**A**: No. Legacy workspace deployments continue working - they automatically become a tenant with KB named "default". See ADR 003 (Backward Compatibility) for migration details.

### Q: What's the performance impact?
**A**: Approximately 5-10% latency overhead (tenant filtering in queries) offset by instance caching (>90% hit rate). Net impact: negligible for most workloads. See ADR 002 (Performance Targets) for details.

### Q: How do we ensure data isolation?
**A**: Defense in depth:
1. **API Layer**: TenantContext dependency validates token and extracts tenant_id
2. **Storage Layer**: All queries auto-filtered by `WHERE tenant_id = ? AND kb_id = ?`
3. **Testing**: Automated tests verify cross-tenant access is denied
See ADR 005 (Threat Model) for complete security analysis.

### Q: Can we support 100+ tenants on one instance?
**A**: Yes. Architecture supports ~100 concurrent cached instances (configurable). For 100+ tenants, use: instance caching (active tenants), database scaling (PostgreSQL replication), and monitoring. See ADR 002 (Known Limitations) for scaling guidance.

### Q: What if a tenant hits the storage quota?
**A**: System enforces ResourceQuota (configurable per tenant). Exceeding quota returns 429 (Too Many Requests). Tenant admin receives alerts. See ADR 003 (ResourceQuota Model) and ADR 004 (Error Handling).

### Q: Can we migrate from workspace without downtime?
**A**: Yes, with dual-write period:
1. Deploy v1.5 (supports both models)
2. Activate background migration job
3. Verify all data migrated
4. Remove workspace support
Total downtime: 0 minutes. See ADR 007 (Migration Strategy).

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## 📞 Getting Help

**Questions about Architecture?**  
→ Review ADR 001, 006 or ask technical lead

**Need Implementation Details?**  
→ See ADR 002 (phased approach) or ADR 003/004 (specs)

**Security Concerns?**  
→ Review ADR 005 (threat model) or contact security team

**Deployment/Operations?**  
→ See ADR 007 (deployment guide, troubleshooting)

**Want to See Alternatives?**  
→ Review ADR 006 (5 alternatives with pros/cons)

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**Document Set Version**: 1.0  
**Last Updated**: 2025-11-20  
**Total Pages**: ~4,000 lines across 7 documents  
**Status**: ✅ Ready for Review and Implementation  
**Next Step**: Schedule ADR review meeting with stakeholders
