Why do teams store HTTP sessions in Redis instead of in Tomcat memory?
PICTURE THIS: GIT FLOW
Simple meaning
In-memory sessions die when the instance dies and they force sticky load balancing.
WHY — Redis instead of guessing?
Why interviewers care about Redis:
on Redis.
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:
- 1In-memory sessions die when
the instance dies and they force sticky load balancing.
- 2Redis is shared, so
any app node can serve the next request.
- 3You still replicate Redis
and set sensible TTLs so idle logins expire.
- 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
In-memory sessions die when the instance dies and they force sticky load balancing. Redis is shared, so any app node can serve the next request.