Comment by mnahkies

The worst / most amusing example of this I've seen in the wild was a third party line of business application that was sequentially triaging "pending tasks" to assign priority/to workers.

Our cloud provider had an aircon/overheating incident in the region we were using, and after it was resolved network latency between the database and application increased by a few milliseconds. Turns out if you multiply that by a few million/fast arrival rate you get a significant amount of time, and the pending tasks queue backs up causing the high priority tasks to be delayed.

Based on the traces we had it looked like a classic case of "ORM made it easy to do it this way, and it works fine until it doesn't" but was unfortunately out of our control being a third party product.

If they'd fetched/processed batches of tasks from the database instead I'm confident it wouldn't have been an issue.