You have to consider that AWS Lambda does have "cold start" - if your code wasn't run for about 10 minutes it isn't "hot" anymore and will have a penalty time cost to its first next request. This is not billable but it is a latency, explained here [1]
Yes it's exactly like FastCGI ... if you make enough requests, then you have a warm process.
If you don't, then you may need to warm one up, and wait.
So yeah I think AWS Lambda and all "serverless" clouds should have been based on an open standard.
But TBH FastCGI is not perfect, as I note in my blog post.
The real problem is that doing standards is harder than not doing them. It's easier to write a proprietary system.
And people aren't incentivized to do that work anymore. (Or really they never were -- the Internet was funded by the US government, and the web came out of CERN ... not out of tech companies)
The best we can get is something like a big tightly-coupled Docker thing, and then Red Hat re-implements it with podman.
[1] https://docs.aws.amazon.com/lambda/latest/operatorguide/exec...