When people talk about scaling requirements they are not referring to minutiae like "this function needs X CPU per request and this other function needs Y CPU per request", they are talking about whether particular endpoints are primarily constrained by different things (i.e. CPU vs memory vs disk). This is important because if I need to scale up machines for one endpoint that requires X CPU but the same service has another endpoint requiring Y memory whereas my original service only needs Z memory and Y is significantly larger than Z then suddenly you have to pay a bunch of extra money to scale up your CPU-bound endpoint because you are co-hosting it with a memory-bound endpoint.
If all your endpoints just do some different logic and all hit a few redis endpoints, run a few postgres queries, and assemble results then keep them all together!!!
EDIT: my original post even included the phrase "significantly different" to describe when you should split a service!!! It's like you decided to have an argument with someone else you've met in your life, but directed it at me
I think I get your point: e.g. some part of your application absolutely needs the world's fastest NVMe as its local disk. Another part of your application just needs more cores from horizontal scaling. If you horiz scale to get more cores, you're also paying to put the world's fastest NVMe on each new machine.
Eh... I think you can achieve this in a simpler way with asymmetric scaling groups and smartly routing workloads to the right group. I feel like it's an ops/infra problem. There's no reason to constrain the underlying infra to be homogenous.
When people talk about scaling requirements they are not referring to minutiae like "this function needs X CPU per request and this other function needs Y CPU per request", they are talking about whether particular endpoints are primarily constrained by different things (i.e. CPU vs memory vs disk). This is important because if I need to scale up machines for one endpoint that requires X CPU but the same service has another endpoint requiring Y memory whereas my original service only needs Z memory and Y is significantly larger than Z then suddenly you have to pay a bunch of extra money to scale up your CPU-bound endpoint because you are co-hosting it with a memory-bound endpoint.
If all your endpoints just do some different logic and all hit a few redis endpoints, run a few postgres queries, and assemble results then keep them all together!!!
EDIT: my original post even included the phrase "significantly different" to describe when you should split a service!!! It's like you decided to have an argument with someone else you've met in your life, but directed it at me