A client's checkout endpoint had idempotency keys. Customers still got double-charged during flash sales. The bug was a three-line race condition between SELECT and INSERT that took two weeks to find.
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Hello, I'm Luke
Applied AI architecture, agent harnesses, and notes from getting AI systems into production.
Latest Posts
- A client was six months into migrating from REST to GraphQL. Half their endpoints were converted, developer experience was arguably worse, and the frontend team was maintaining two data layers. Sometimes the right engineering decision is to stop.
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- We ran a data backfill on 140,000 subscription records while the app was live. Three weeks later, 1,800 customers had the wrong renewal date. The script looked fine. The bug was in the timing.
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- On-call never shows up in exit interviews. But across half a dozen consulting engagements, I've watched it quietly hollow out engineering teams. The pattern is always the same, and it's always fixable.
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- Every 30 minutes, the auth server spiked to 100% CPU and shed requests. The pattern was so regular you could set a watch by it. Turned out every user's JWT expired at the same time.
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