I have a Postgres dyno on Heroku and I use Datadog.
Two postgres dashboards are by default on Datadog: Metrics and Overview.
Metrics is working (CPU usage, memory, I/O,...) but Overview is not (deadlocks, indexes usages)
Are Heroku Postgres dyno and Datadog fully compatible?
There are a number of ways you can get metrics out of the box into datadog for your application or service.
Assuming you are using a backend service since you described postgres, you can use one of the many datadog dependencies. One such for node applications i use is dd-trace, it has a number of different plugins for postgres (connections using the pg library) out of the box. Although these give you a lot of metrics about querys ran and help identify application level bottlenecks, you will need to do additional work to get other things like deadlocks, indexes usages, and connected users into datadog. Two main ways to go about this,