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#concurrency
2 posts
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[Messenger Load-Testing, Part 3] FCM to a Queue, Swallowed Failures to Sentry — Cleaning Up the Message-Send Handler
Part 3 of load-testing a messenger: pulling FCM push out of the message-send handler into a dedicated worker queue, and surfacing the failures that used to vanish into empty catches through Sentry. Two axes — isolating external I/O and handling error logs.
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[Messenger Load-Testing, Part 2] There Was a Deadlock Hiding in AI-Generated Code — How We Replaced `unreadCount` with `lastReadAt`
42.8% HTTP error rate, 9 minutes into a load test, at 12% of the target TPS. The culprit was a single updateMany line written during AI-assisted coding.
