Stateless And Stateful Service

Stateless And Stateful Service

Stateless vs stateful services and their scaling implications.

STATELESS Stateless services don’t save any user info between requests. This means any server can handle any request — super easy to add more servers (horizontal scaling).

STATEFUL Stateful services keep user info (state) between requests. So requests must go to the same server that has the user’s data, which makes scaling harder.

Stateless and Stateful Service

Imagine a login API where every request includes your username and password. The server checks your credentials and responds. It doesn’t remember anything between requests. Any server can handle your login request.

Imagine a shopping cart on an e-commerce site that keeps your cart items stored in the server’s memory during your visit. You must talk to the same server to keep your cart updated.

| Service Type | Best Scaling Method | Why? | | ------------ | ------------------------------------- | ---------------------------------------------------------- | | Stateless | Horizontal Scaling | Easy to add/remove servers freely | | Stateful | Vertical Scaling* / Externalize State | Hard to spread state; vertical scaling easier, but limited |