Amazon RDS db connects locally but not on production

I was able to connect to the amazon rds aurora database locally, and run queries.

But on production EC2 server, the connection returns 500 server error "SQLSTATE[HY000] [2002] Connection timed out".

• I've added the same credentials for the database to production, and can see they are being used in the error log.
• I enabled the 'allow public access' setting.
• I added all the security groups I have to the database (this is probably the problem, I didnt create any special groups, just whatever amazon suggested I let them do).

How could it be working locally but not on production?

It was a security group issue.

The default rds-setup-wizard security group was applied to my database instance, and this gave me local access. I guess it had my ip address or similar as an inbound rule.

I had to add a new security group and add that new group to the database instance.

My new security group needed an inbound rule that looked like this:

Type: MYSQL/Aurora
Protocol: TCP
Port Range: 3306
Source: my EC2's private ipv4 address with /32. Eg: 13.14.15.16/32