AWS EC2 Private Instance DB Connection

Question

I have a VPC with public & private subnets (Windows 2019). I installed Postgres database (not RDS) manually in the private instance. As recommended by AWS I have created all the security group rules in public & private instance security groups. I wasn't able to connect to the DB from public instance. Please advise. Thanks.

Public instance security group:

• HTTP TCP 80 0.0.0.0/0 -
• PostgreSQL TCP 5432 0.0.0.0/0
• RDP TCP 3389 0.0.0.0/0 -
• HTTPS TCP 443 0.0.0.0/0

Outbound:

• PostgreSQL TCP 5432 sg-0f189eca6a0f783dd (PRIVATE-SG)

Private instance security group:

• PostgreSQL TCP 5432 sg-008ffcfcdec814a91 (PUBLIC-SG)
• RDP TCP 3389 sg-008ffcfcdec814a91 (PUBLIC-SG)

Answer 1

Based on the comments.

The connection issue was caused by build-in firewall on Windows instances.

The solution was to add rule to the firewall enabling port 5432.