There are several key metrics that you will definitely want to keep track of when it comes to database performance, and they are not all database-specific.
You should keep track of shared buffer usage while reading or updating data. In the shared buffer cache, PostgreSQL checks for the execution of a request. It will take data from the disk if the block is not found in the shared buffer cache. Once this is done, the data will be cached in the shared buffer cache of the database.
Implementing effective database monitoring can offer benefits such as increasing performance, increasing the availability of the application, faster database outage detection, and accurately analyzing storage requirements and index performance.