>meaning each request must take substantially less than 10 ms

Correction, each request would need to have less than 10ms of CPU time - the instances support concurrency.

My web frontend, by design, does very little - any CPU heavy operations are done by other systems using the task queue. Writing it in golang has helped as well, wouldn't get that performance from python.

Write a simple Hello world example in golang and get it to do some mathematical calculations to simulate "work", I think you'll be surprised at how many requests a second you can squeeze out of a single instance.