Redis Memory Debugging Guide
Debug Redis memory pressure with INFO, maxmemory policy, keyspace evidence, big keys and safer cache incident notes. This Formalint reference is written for working developers, DBAs and support engineers who need a repeatable debugging path instead of a one-line snippet with no context.
Use the notes below as a practical review order: understand the input, capture evidence, make one small change and verify the result before moving to the next assumption.
When to use this page
Find Redis memory pressure before deleting keys in a hurry. It is most useful when a small validation or debugging mistake can create noisy tickets, misleading logs or hard-to-review production changes.
Practical workflow
| Step | What to confirm |
|---|---|
| Capture memory first | Save used_memory, maxmemory and policy before changes. |
| Find key patterns | Look for large keys, unbounded prefixes and missing TTLs. |
| Protect production | Avoid expensive scans during peak traffic without a plan. |
Redis memory checks
redis-cli INFO memory
redis-cli CONFIG GET maxmemory
redis-cli CONFIG GET maxmemory-policy
redis-cli --bigkeysReview checklist
- Check eviction policy and whether evictions are happening.
- Inspect TTL coverage for cache keys.
- Look for sudden client growth or connection leaks.
- Measure big keys in a safe window.
- Confirm whether Redis is cache, queue, session store or primary data.
Common mistake
Deleting a big key can fix memory briefly while the application immediately recreates it. Find the producing code path.
Formalint is strongest when the page helps the developer decide what the tool cannot prove. Treat every formatter, regex and command as one layer of evidence, not the whole truth.
Frequently asked questions
Is Redis memory high always bad?
Not necessarily. Redis is designed to use memory, but maxmemory, eviction and growth rate matter.
Should I run KEYS in production?
Avoid it on large instances. Prefer safer scanning and controlled diagnostics.
Related Formalint references
Continue with Redis Debugging Checklist, Hardware Diagnostics, Api Timeout Debugging Guide.