Nextcloud asked in a poll at https://mastodon.social/@nextcloud@mastodon.xyz/115095096413238457 what database its users are running. Interestingly one fifth replied they don’t know. Should people know better where their data is stored, or is it a good thing everything is running so smoothly people don’t need to know what their software stack is built upon?
I disagree. You are just entertaining the idea that servers must always and forever be oversized, that’s the definition of wasteful (and environmentally irresponsible). Unless you are firing-up and throwing-away services constantly, nothing justifies this and sparing the relatively low effort it is to deploy your infrastructure knowingly.
Do you have the data to back that up? Have you measured how much of an impact on system load and power consumption having 2 separate DB processes has?
Roughly the same amount of work is being done by the CPU if you split your DBs between 2 servers or just use one. There might be a slight increase in memory usage, but that would only matter in a few niche applications and wouldn’t affect environmental impact.