Databases
Environment
Environment
Redis 7 used as a cache for a Node.js API in Docker.
What happens
What happens
Key count falls after expiry but RSS memory stays close to the previous peak.
What I have tried
What I have tried
Confirmed TTLs and checked that no persistent keys are accumulating.
I would appreciate advice on how to identify the root cause without risking existing data or configuration.
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AI DIAGNOSTICS
Incident analysis
Most likely causes
Allocator fragmentation retains freed pages rather than immediately returning them to the OS. 87%
A recent software, firmware or configuration change is exposing an existing compatibility issue. 41%
Summary
The reported behaviour is consistent with allocator fragmentation retains freed pages rather than immediately returning them to the OS. The safest next step is to verify that hypothesis with a reversible test before making permanent configuration changes.
Suggested Fixes
Verify the likely cause
Compare used_memory and used_memory_rss, enable active defragmentation when appropriate and set a tested maxmemory eviction policy.
Validate and monitor
Reproduce the issue once after the change, review relevant logs or metrics, and keep a rollback path until the system has remained stable.