[Dylan16807]

> as well as reduces the 99th percentile latency

How does it manage to do that?

When you're getting close to your limits and requests are actually waiting in the queue, I would expect FIFO to slow down everything to provide backpressure, while LIFO keeps a very nice median speed but has an increasing percentage of requests that timeout and retry once or even twice.

Are there significant dynamics I'm not thinking of?

Maybe if you have bursts that are just big enough for FIFO to delay >1% of total requests, but small enough for LIFO to drop <1%? But in that situation giving a single percentile paints a misleading picture; 99th would do better on LIFO but it comes at the cost of trashing higher percentiles.