[fulafel]

Certs is a standard feature. IAM doesn't require nonstandard client or protocol features either (see https://aws.amazon.com/premiumsupport/knowledge-center/users...).

I think with client certs work fine with SQL Server and Oracle too, with standard clients.

But I'm sure you can come up with imagined scenarios where you end up cornered to use VPCs. I get it, these situations may exist. I'm just saying they suck, not that you'll never have to resort to them.