Two Spellings of One Instant
A claim token written as a JavaScript timestamp ending in Z came back from Postgres ending in +00:00. The run compared them as strings, decided the claim was stale, and exited. Every time. The tests passed because they used tidy fake tokens.
An Unordered Limit Is a Lottery
A scheduled job ran green every thirty minutes for a week and did almost nothing, because its query had a LIMIT and no ORDER BY. An audit found the same shape in nine other jobs, two of them already starving real work.
The Row That Never Finished
Activity rows left as running by processes that died were counted by a concurrency gate forever. Two of them made every image wait a full minute and then carry on, which is why nothing ever reported it.
Two Workers, One Frame
Two render requests could both read a frame as idle, both claim it, and both charge for it. The fix was to stop treating a status write as the record of a decision and make it the decision itself.