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Engineering notes
Notes on things that broke, things I measured, and what I’d do differently next time.
2026
- 2 min read
One writer, checked on every connection. HAProxy in front of 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.
- 2 min read
The stutters that weren't the code
A single-threaded server kept freezing and the application looked guilty. Counting page faults per frame pointed somewhere else entirely.
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