Will I reach Heroku's Postgres Connection Limit?

Question

I want to sanity check my understanding of Heroku's Postgres Connection Limit.

I currently use the Postgres Standard 0 addon which has a Connection Limit of 120. I am also running a Django application in two Standard 1x dynos. Each dyno runs the application using gunicorn with two workers.

So firstly am I correct in assuming my application can handle four requests at any one time?

Second will I ever reach the Postgres Connection Limit? I assuming not as there will only ever be four connections to Postgres at any one time.

Answer 1

The answer is no, I won't run into the Postgres Connection Limit with this setup. At most there will four connections to Postgres.

Heroku have gone into detail this here https://devcenter.heroku.com/articles/python-concurrency-and-database-connections

I think the only time you need to worry about reaching the connection limit is if you are using an async server.

Answer 2

Your best bet is to either use connection pooling via an ORM, or pgbouncer. I wrote my own async threaded connection for psycopg2.

You can find my code in this answer here:

Python Postgres psycopg2 ThreadedConnectionPool exhausted