Comment by hombre_fatal

On the other hand, there is a real crossroad that pops up that HNers tend to dismiss.

A common story is that since day one you just have lightweight app servers handling http requests doing 99% I/O. And your app servers can be deployed on a cheap box anywhere since they're just doing I/O. Maybe they're on Google Cloud Run or a small cluster of $5 VPS. You've built them so that they have zero deps on the machine they're running on.

But then one day you need to do some sort of computations.

One incremental option is to create a worker that can sit on a machine that can crunch the tasks and a pipeline to feed it. This can be seen as operationally complex compared to one machine, but it's also simple in other ways.

Another option is to do everything on one beefy server where your app servers just shell out the work on the same machine. This can be operationally simple in some ways, but not necessarily in all ways.