> Ease of use is nice for a start, but usually becomes technical debt.

The difference with the Express ecosystem is that you aren't getting any less power than with FastAPI or Spring Boot, you just get less overhead. Spring Boot has 10x the config to get the same endpoint up and running as Express, and FastAPI has at least 3x the magic. Now some of FastAPI's magic is really useful (auto converting pydantic types to JSON Schemas on endpoints, auto generating API docs, etc), but it is still magic compared to what Express gets you.

The scaling story of Node is also really easy to think about and do capacity planning for. You aren't worried about contention or IPC (as this thread has pointed out, if you are doing IPC in Node you are in for a bad time, so just don't!), your unit of scaling is the Node process itself. Throw it in a docker image, throw that in a k8s cluster, assign .25 CPU to each instance. Scale up and down as needed.

Sometimes having one really damn simple and easy to understand building block is more powerful than having 500 blocks that can be misconfigured in ten thousand different ways.