Postgresql is amongst the safest Open Source database. Rock solid and simple to maintain - year after year. In my case it is used both as a "lookup" database (static contents) and as a "real" database (CRUD contents). The lookup database should be on localhost, but the CRUD database can be on another VPS. Note that Upcloud can connect to this "external" database by a local IP adress. Every VPS on Upcloud have 2 IP-addresses. The internal IP-address can be reach only from another VPS not reachable from outside internet.
Log in to Webmin and install Postgres with one click:
Refresh Moduls to reach the Webmin Postgresql Manager
To administer Postgresql I recommend pgAdmin installed on your local computer. It is way better than Webmin Postgresql Manager. Note that you must edit /etc/postgresql/11/main/postgresql.conf :
listen_addresses = '*' # what IP address(es) to listen on;
Here is the link to download pgAdmin:Download pgAdmin