For the best performance, the values for the initial, minimal and maximum database connection pool size should all be equal.
This avoids creating new database connections when a new request comes in which is costly.

Keeping the database connection open for as long as possible allows for server side statement caching bound to a connection.
In the case of PostgreSQL, to use a server-side prepared statement, https://jdbc.postgresql.org/documentation/server-prepare/#activation[a query needs to be executed (by default) at least five times].

See the https://www.postgresql.org/docs/current/sql-prepare.html[PostgreSQL docs on prepared statements] for more information.