What happens to the database load if the connection is left open and no queries are sent?

If you leave the connection to the database open but do not execute any queries, the load on the database will be minimal, as an open session without activity does not require significant resources. However, such open connections consume resources of the database server (for example, memory and connection descriptors), which can lead to exhaustion of available connections when there are many such 'idle' sessions. This can reduce overall performance and cause errors when attempting to establish new connections. Therefore, it is recommended to close unused connections or use a connection pool with a timeout for inactive sessions.