How to increase number of "VPCs per region" from 5 to 15 ?

To increase the number of VPCs per region from 5 to 15, you'll need to request a service quota increase from AWS. Here's how you can do it:

1. Open the AWS Service Quotas console or use the AWS Command Line Interface (CLI).

2. Look for the "Amazon Virtual Private Cloud (Amazon VPC)" service, not "Amazon Elastic Compute Cloud (Amazon EC2)". The VPC quota is listed under the VPC service, not EC2.

3. Find the quota named "VPCs per Region" with the default value of 5.

4. Request an increase for this quota to 15. You may need to provide a justification for the increase.

5. AWS will review your request and typically respond within a few business days.

If you don't see the "VPCs per Region" quota listed, you can open a support case through the AWS Support Center Console to request the increase.

It's worth noting that increasing this quota also increases the quota on internet gateways per Region by the same amount. AWS allows for hundreds of VPCs per Region, so increasing to 15 should be possible.

Remember, while you're able to increase this limit significantly, it's important to consider the management overhead and potential costs associated with running multiple VPCs in a single region.
Sources
Amazon VPC quotas - Amazon Virtual Private Cloud
Networking 101 - Part 3 | AWS re:Post