fizi.pw engineering notesNotes by Tomasz Gradek on infrastructure, performance, databases and operations.https://fizi.pw/enOne writer, checked on every connection. HAProxy in front of Sentinelhttps://fizi.pw/blog/one-writer-haproxy-valkey-sentinel/https://fizi.pw/blog/one-writer-haproxy-valkey-sentinel/Why asking a Redis-compatible node for its role isn't enough after a failover, and how one HAProxy health check can ask Sentinel and the node at the same time.Wed, 07 Oct 2026 00:00:00 GMTValkeyHAProxyHigh availabilityThe stutters that weren't the codehttps://fizi.pw/blog/hitches-that-were-not-plugins/https://fizi.pw/blog/hitches-that-were-not-plugins/A single-threaded server kept freezing and the application looked guilty. Counting page faults per frame pointed somewhere else entirely.Tue, 06 Oct 2026 00:00:00 GMTLinuxPerformanceProfiling