Heroku keeps track of all kinds of diagnostics on the performance of your app's database. From long running queries and transactions to index cache hit rates to unused indexes to tables with bloat.
Running the pg:diagnose command for your Heroku app will surface all of these
details in the terminal.
$ heroku pg:diagnose -a APP_NAMEThe report will start with the biggest problem areas which it color codes in red. If your app is experiencing degraded performance, the list of red items would be a good place to start investigating.
The report will then list less urgent problem areas. Those will be color coded yellow. Though Heroku has deemed these less serious, you may still want to deal with these.
All the other areas of diagnose will fall into the green bucket. Meaning Heroku doesn't see any issues in those areas.