How is a cache different from your primary database?
PICTURE THIS: DATABASE INDEX
Simple meaning
The database is the system of record and is built for durability and queries.
WHY — Redis instead of guessing?
Why interviewers care about Redis:
who only read docs from people who shipped.
and tied to Backend work.
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:
- 1The database is the
system of record and is built for durability and queries.
- 2A cache is a
speed layer that may be stale or missing.
- 3If Redis is down,
the service should still work, just slower, unless you designed Redis as a required data store.
- 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
The database is the system of record and is built for durability and queries. A cache is a speed layer that may be stale or missing.