Why are sticky sessions a scaling smell, and what do you do instead?
PICTURE THIS: HOW TO EXPLAIN IT
Simple meaning
Stickiness pins a user to one instance so in-memory session state works, which defeats even load and complicates deploys.
WHY — Load balancer instead of guessing?
Why interviewers care about Load balancer:
on Load balancer.
the situation, the default choice, and one exception - that reads as experience.
Name the idea, why it exists, then one short example.
End with when you use it and one common pitfall.
STEPS — What happens step by step?
Before you speak the answer, walk the interviewer through these steps:
- 1Stickiness pins a user
to one instance so in-memory session state works, which defeats even load and complicates deploys.
- 2Put session data in
Redis or use JWTs so any node can serve the request.
- 3Keep stickiness only as
a short migration crutch.
- 4Give an example
One tiny concrete case you can say aloud.
- 5Common mistake
What juniors usually get wrong.
- 6Close
When you pick this over the alternative.
EXAMPLE — See it in action
Here's a short line you can speak, broken into clear beats:
Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.
Key takeaway
Stickiness pins a user to one instance so in-memory session state works, which defeats even load and complicates deploys. Put session data in Redis or use JWTs so any node can serve the request.