LangChain Reference Architecture

Overview

Production architectural patterns for LangChain: layered project structure, provider abstraction for vendor flexibility, chain registry for dynamic management, RAG architecture, and multi-agent orchestration.

Layered Architecture

src/
├── api/                    # HTTP layer (Express/Fastify/FastAPI)
│   ├── routes/
│   │   ├── chat.ts         # POST /api/chat, /api/chat/stream
│   │   └── documents.ts    # POST /api/documents/ingest
│   └── middleware/
│       ├── auth.ts         # JWT/OAuth validation
│       └── rateLimit.ts    # Per-user rate limiting
├── core/                   # Business logic (pure, testable)
│   ├── chains/
│   │   ├── summarize.ts    # Summarize chain factory