> Ideally, we would have used JMeter or something similar, but we could not get it to run locally. So we wrote a small script to walk through most of our endpoints, with concurrent requests, ramp-up time, the works.

I'm pretty sure somewhere north of 80% of load testing tasks play out exactly like this - certainly at least 4 or 5 of these efforts that I've been a part of started with an attempt to get the latest version of JMeter to work ("we should use the mature solution and not reinvent the wheel, right?"), hit major difficulties, and ended up with me cobbling together an ugly but working 100 LoC script that did the job with far fewer headaches than the feature-rich but not really functional Cadillac solutions out there. Apache Bench can do quite a bit in a pinch, and doesn't choke up as quickly as a lot of other ways that you might generate traffic.

Re: Cloud Functions vs. Cloud Run, both are fantastic services and I do tend to prefer Cloud Run lately. For minimizing cold start latency another trick you can use if that's too big a move is to do your function routing within a single global endpoint (obviously this only works for internal-only APIs) - rather than having 100+ endpoints that you hit, you always hit the same endpoint and just include the desired call as a parameter, and route to the correct logic in a few extra lines of code. With all your functionality now passing through the same cloud function call, you're much less likely to incur the cold start penalty on your less frequently called functions, though it comes at the cost of some complexity in code. If you're going through Firebase it also speeds up your deployments quite a bit because you only have 1 function to deploy. Not a silver bullet (and it's also not a good solution if you want a proper REST API, since you're basically forced to jam everything through a POST endpoint), but can be an effective intermediate workaround if going all the way to Cloud Run is too daunting.