You are right. The best solution is separation of services. But for a startup than runs 7-2 services like this – it’s a close call. You’ll often have to run 2-3 services together, else $100 * 7 machines is too much burn
It's not a problem running several services on the same box as soon as each of them is sized appropriately. What I suggest at least roughly calculate how much eg. RAM could each service use at peak time. This usage should be limited so that the sum of memory used by all services at peak time is less than the amount of RAM you've got on your server.
