What's the worst bug you've traced back to Kafka partitioning/key choice?

Curious what people have actually hit in production - messages landing in an unexpected partition, ordering breaking because of a key choice made early and never revisited, a 'random' bug that turned out to be perfectly deterministic once you understood the hashing. What was the actual symptom before you knew the cause, and what was the fix — repartition, change the key, something else? submitted by /u/Altruistic_Shift_335 [link] [comments]