NoSQLIntermediate
When should you NOT use Redis?
“What are Redis’s limits, and what should never live only in it?”
What this tests
- Durability limits
- Memory limits
- Query limits
Answers by level
Read the beginner answer first and notice what is missing.
Not as the system of record for anything you cannot lose — persistence is partial (AOF everysec loses up to a second; always costs most of the throughput). Not for data larger than memory. Not for queries by anything other than key — there is no WHERE clause. Not for multi-key transactions with rollback.
And the eviction policy matters: the default noeviction turns a full cache into write failures.
Green flags · Red flags
Strong green flag · States "never the only copy of anything you cannot lose".
Green flags
- Durability caveats
- Memory and query limits
- Eviction policy awareness
Red flags
- Treats Redis as durable
- Unaware of the memory ceiling
Follow-up questions
F1
What eviction policy for a pure cache, and what is the danger of the default?
Scenario
A team stores the only copy of shopping carts in Redis with no persistence tuning. What is the risk?