The condition was inverted - it was caching lookups with errors
instead of successful lookups. This caused every replicated write
to make a gRPC call to master for volume location lookup, resulting
in ~1 second latency for writeToReplicas.
The bug particularly affected TTL volumes because:
- More unique volumes are created (separate pools per TTL)
- Volumes expire and get recreated frequently
- Each new volume requires a fresh lookup (cache miss)
- Higher volume churn = more cache misses = more master lookups
With this fix, successful lookups are cached for 10 minutes,
reducing replication latency from ~1s to ~10ms for cached volumes.
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