@whitequark As people noted, the data is a bit thin, maybe throw some k6, siege or ab traffic at it? But (assuming it's impossible to get better data): * You have some weird latency going on already between frontend and backend (_sometimes_ BE is <10ms, yet corresponding FE is >50ms). If it's the same machine, I'd check CPU and I/O load, if not, network overload between them? * During a latency spike there are _no_ fast requests. Likely they all blocked on the same resource. You could verify this by checking the request logs and see if they all completed at nearly the same time (but started differently). * If this is still static-from-S3, maybe consider https://docs.aws.amazon.com/AmazonS3/latest/userguide/optimizing-performance-guidelines.html#optimizing-performance-guidelines-retry and just fire of every request to S3 a bunch of times and take the earliest answer.