Statelessness in REST APIs

What is Statelessness in REST APIs?

Statelessness is a core principle of REST (Representational State Transfer) that ensures each request from a client to the server is independent and does not rely on previous requests.

💡 Key Idea: The server does not store client session data between requests. Each API call must contain all necessary information to process the request.

🔹 Why is Statelessness Important?

✅ Scalability — No session data allows easy horizontal scaling.
✅ Reliability — No session storage eliminates session-related failures.
✅ Simplicity — Easier debugging and stateless services.
✅ Better Caching — Stateless APIs work well with caching mechanisms.

📌 Example Scenario Without Statelessness:
1️⃣ Client: Sends request to /checkout
2️⃣ Server: Stores user session (userId=123)
3️⃣ Client: Sends another request without credentials
4️⃣ Server: Retrieves session from memory

❌ Problem: If the server crashes, session data is lost, breaking the flow.

📌 Example Scenario With Statelessness:
1️⃣ Client: Sends request to /checkout with all required data

POST /checkout
Authorization: Bearer token_abc123
{
  "userId": 123,
  "cart"…