Importance:?

Short answer: Stateful Services: If a service needs to keep track of user state (e.g., user preferences, shopping carts), sticky sessions ensure the user’s requests are directed to the same instance, preventing session data loss.

Explain a bit more

Consistency: In systems with user sessions (e.g., e-commerce platforms), ensuring that all requests from a user go to the same instance prevents inconsistencies in data retrieval. Example: In an Authentication Service, where a user logs in and the session is maintained on the instance, sticky sessions ensure that subsequent requests from that user are routed to the same service instance.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.