Here's an issue tracking digitalocean database issues--some managed databases don't work right now: https://github.com/FusionAuth/fusionauth-issues/issues/95
The number of open connections should be around 10. I believe that is per fusionauth instance.
What were the specs you were seeing the issues with?what version of fusionauth how many pods running it what version of postgres what size were the pods (in terms of memory and CPU) what are the replication steps to trigger the negative performance impacts
We've seen FusionAuth (the application) run in 64M of RAM. You can specify the maximum amount of memory used in the configuration file or via environment args. More here: https://fusionauth.io/docs/v1/tech/reference/configuration
Note that if you don't need advanced search functionality, you can use the database search engine and avoid running elasticsearch: https://fusionauth.io/docs/v1/tech/tutorials/switch-search-engines talks about how to switch between them. That may eliminate some of the memory pressure if you were running elastic.