Why are sticky sessions valuable for a load-balanced e-commerce site?

• A. Sticky sessions
• B. Round-robin by IP
• C. DDoS protection
• D. Basic health checks

Answer: (A)

Sticky sessions, or session affinity, keep a user’s requests on the same backend server during a session. For an e-commerce site, a lot of the shopping experience depends on in-memory session data like the shopping cart contents, login state, and checkout progress. If each request could land on any server, that in-memory data might not be available on the new server, leading to missing cart items, repeated logins, or disrupted checkout flows. By routing a user to a single server, that data stays readily accessible, delivering faster responses, a smoother checkout, and simpler session management without needing to constantly synchronize session data across all servers.

Of course, there are trade-offs: if the chosen server fails, the session can be lost unless you have a shared session store or robust failover; and sticky sessions can cause uneven load if not balanced properly. But the key value is preserving the user’s session state on the server handling their requests, which is especially important during checkout. Round-robin by IP would spread requests without guaranteeing state continuity, and DDoS protection or basic health checks address different concerns.