Connection pooling - NodeJS or Database products? Consider the mysql package. The description covers connection pooling thus, 


  Rather than creating and managing connections one-by-one, this module
  also provides built-in connection pooling using
  mysql.createPool(config).


Then, there is the connection pool setting in proxysql as described here.

Similarly, in case of PostgreSQL too, there is the pg package supporting connection pooling and pgboucner pooling feature.


How are these approaches (npm package versus product supporting tools) different?
Ideally, I would like to configure connection pooling at the database level so that a developer is free from handling connections. Can this be a preferred approach?
You can use connection pooling on any level, but I believe that it is best done with a connection pool inside the application server code for these reasons:


You don't need an extra process like pgBouncer that you have start and monitor.
You don't have any more TCP connections than necessary, thus conserving resources and being faster.


This holds if you have a single application server. If several of them access the same database, connecting pooling in the application server isn't enough. It is still a goid idea if you want to limit the DB resources each one can use, but you will still need another connection pool to limit the total number of database connections.

Such a connection pool can be implemented in the database if the RDBMS supports it (PostgreSQL doesn't), or it can be an external tool like pgBouncer.