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🧱 Stateless Architecture
Stateless Architecture is a foundational concept for scalable and resilient systems, especially in cloud-native and distributed environments.
📘 1. What is Stateless Architecture?
A stateless system does not store client or session information between requests. Each request is independent, self-contained, and carries all necessary context.
🔄 2. Stateless vs Stateful
| Aspect | Stateless | Stateful |
|---|---|---|
| Request Memory | No memory of previous requests | Maintains context across requests |
| Scalability | Easier to scale | Harder to scale (session affinity needed) |
| Resilience | More fault-tolerant | Susceptible to session loss |
| Examples | REST APIs, Load-balanced Microservices | WebSockets, Online Games, Legacy apps |
🔧 3. Benefits of Stateless Architecture
- ✅ Easy horizontal scaling
- 🔄 Better fault tolerance
- 🧪 Simplified testing
- ☁️ Cloud-native compatibility
- 🔐 Improved security (less stored state to compromise)
🚧 4. Challenges of Statelessness
- Handling user sessions (authentication, carts)
- Handling long-running workflows
- Need to move session/state to external systems (e.g. databases, caches, tokens)
🛠️ 5. Patterns to Achieve Statelessness
🔐 Token-based Authentication
Use JWT or PASETO tokens that carry user data in each request.
Authorization: Bearer <jwt_token>
🧠 External State Management
Move session data to external stores like:
- Redis (caching)
- RDBMS or NoSQL (persistent session state)
📨 Idempotency
Ensure APIs can safely retry without side effects.
POST /orders
Idempotency-Key: 12345-abcde
🧰 6. Stateless Technologies
| Area | Technologies |
|---|---|
| Auth | JWT, OAuth2, PASETO |
| Caching | Redis, Memcached |
| APIs | REST, GraphQL (stateless by design) |
| Infra | Serverless, Kubernetes, Containers |
🌐 7. Real-World Examples
- REST APIs: Each call is self-contained.
- CDNs: Serve cached resources without user state.
- FaaS: Serverless functions like AWS Lambda are stateless by nature.
🔍 8. When Not to Use Stateless Design
- Real-time communication (e.g. chat, multiplayer games)
- Complex stateful workflows
- Cases where performance relies on local session data
✅ 9. Statelessness Checklist
- [ ] Is all required context included in each request?
- [ ] Is session data stored externally?
- [ ] Are retries idempotent and safe?
- [ ] Is horizontal scaling supported without session stickiness?
- [ ] Is authentication stateless?