AWS PostgreSQL max_connection per instance type

aws_postgresql_max_connection.md

The default formula use by AWS RDS to calculate the max_connections parameter is: LEAST({DBInstanceClassMemory/9531392},5000)

But It's hard to find the exact value of DBInstanceClassMemory.

So, here are the values I got when I ran the SQL commmand: show max_connections; in some RDS instances:

Instance type	RAM (GB)	max_connections
db.t2.small	2	198
db.t2.medium	4	413
db.t2.large	8	856
db.m4.large	8	856
db.r4.large	15.25	1660

These are default values. You can always change the max_connections value in the parameters group of your DB.

You can use the query below to collect the value that is the result of the equation LEAST({DBInstanceClassMemory/9531392},5000)

select * from pg_settings where name='max_connections';

max_connections is the result of an equation

In some cases, depending on the way your system was built, you may end up reaching 100% CPU usage before you even reach half of the possible connections.
keep your eyes open for this.

Does this LEAST({DBInstanceClassMemory/9531392},5000) apply to graviton instances too. As it seems they support more max connections than the others based on https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/AuroraPostgreSQL.Managing.html but doesn't have data for t4g family.

Graviton - db.r6g.xlarge (32 GB) = 3484. Looks like the same formula.