🏗️ Common Architecture
১. Single-shot
User → API → LLM → Response
// Translate, summarize, classify
২. Conversational
User → API → [History + LLM] → Response
↓
Save state
৩. RAG
User → Query
↓
Embed → Vector DB → Top-K
↓
[Context + Query] → LLM → Answer + Citation
৪. Agent
User → Goal
↓
[Plan → Tool → Observe] loop
↓
Final Answer
৫. Pipeline
Step 1: Classifier (cheap model)
↓
Step 2: Router (which expert?)
↓
Step 3: Specialized prompt
↓
Step 4: Validator
↓
Step 5: Format output
🧠 State Management
- Stateless — every request standalone (simplest)
- Session — Redis/DB-তে conversation
- User profile — long-term memory
- Tenant — multi-customer isolation
📦 Tech Stack Example
Frontend: Next.js / React
Backend: FastAPI / Express
LLM: OpenAI API / Claude / local
Vector DB: Pinecone / pgvector
Cache: Redis (semantic + response)
Queue: SQS / RabbitMQ (async)
Monitoring: Helicone / LangSmith
Auth: Clerk / Auth0
Storage: S3 (file)
DB: Postgres (metadata)
⚡ Caching Layer ⭐
- Exact match — same prompt → cached response
- Semantic — similar prompt → cached
- Prompt cache (Anthropic) — system prompt
- CDN — static AI output
🔄 Async Processing
- Long task → background job
- Webhook callback
- Streaming for UX
- Queue + worker
- Progress notification
🛡️ Reliability Pattern
- Retry exponential backoff
- Circuit breaker — provider down
- Fallback model — primary fail → secondary
- Multi-provider — OpenAI + Claude switch
- Timeout always
- Validation output
- Graceful degrade
📊 Cost Optimization
- Model routing (cheap default, expensive fallback)
- Caching
- Compression (history summarize)
- Batch API
- Streaming (perceived faster)
- Token limit per user
- Cost monitoring + alert
🔐 Security Layer
- Rate limit (per user, per IP)
- Input sanitize
- Output filter (PII, profanity)
- Auth + authorization
- Audit log
- API key rotation
- Network isolation (private endpoint)
🎯 Production Checklist ⭐
- ☐ Auth + rate limit
- ☐ Input validation
- ☐ Output validation
- ☐ Error handling + retry
- ☐ Timeout
- ☐ Logging + tracing
- ☐ Cost monitoring
- ☐ User feedback collect
- ☐ A/B test infrastructure
- ☐ Fallback model
- ☐ Cache layer
- ☐ Privacy/compliance
- ☐ Documentation
- ☐ Disaster recovery
- ☐ Incident playbook