Sitar-agent: Building a reliable dynamic configuration sidecar at scale

Short summary

Airbnb's Sitar system uses a lightweight Kubernetes sidecar (sitar-agent) to deliver dynamic configuration changes reliably to thousands of service instances without redeployment. The agent preloads snapshots from S3 for fast cold starts, then continuously polls the Sitar Service for updates with jitter. Recent Java rewrite prioritized reliability through filesystem caching with in-memory refresh, strict ACL enforcement, and graceful degradation when the control plane is unavailable.

• •Kubernetes sidecar pattern for zero-redeployment config delivery across thousands of pods
• •S3 snapshot preload for fast startup + continuous polling with jitter to prevent thundering herds
• •Java rewrite focused on high reliability, caching strategy, and graceful failure modes

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