Stateless vs Stateful Services#
Stateless services do not retain client-specific state between requests, while stateful services persist session or workflow state. The choice affects scalability, availability, and operational complexity.
Stateless Services#
Benefits:
- Horizontal scaling is straightforward.
- Failover is simple because any instance can serve any request.
- Deployment and autoscaling are low-risk.
Tradeoffs:
- Requires external state stores.
- May increase latency due to extra lookups.
Stateful Services#
Benefits:
- Lower latency when state is local.
- Simplifies complex workflows that rely on in-memory state.
Tradeoffs:
- Harder to scale and fail over.
- Requires session affinity or sticky routing.
- More complex deployment strategies.
Spring Boot Example: Externalized Session State#
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@Configuration
@EnableRedisHttpSession
public class SessionConfig {
}
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@RestController
@RequestMapping("/cart")
public class CartController {
@PostMapping("/items")
public ResponseEntity<Void> addItem(HttpSession session) {
List<String> items = (List<String>) session.getAttribute("items");
if (items == null) {
items = new ArrayList<>();
}
items.add("item-1");
session.setAttribute("items", items);
return ResponseEntity.ok().build();
}
}
Summary#
Stateless services are easier to scale and operate, while stateful services can offer lower latency for specific workflows. Externalizing state often provides the best balance for modern cloud architectures.