InsufficientDBInstanceCapacity Sydney Region

Can I get someone from AWS to comment on this?

I have purchased a new RDS RI for a multiaz t3.micro and I am unable to deploy it due to insufficient capacity. Why am I able to purchase an RI with specs that you are currently unable to provide?

The forum is for community discussion and AWS participation is intermittent at best. You may need to contact support for help. Even if you don't have Premium Support, by purchasing an RI that they can't seem to deliver you could submit an "Account and Billing Support" request.

It is unlikely to be an actual capacity problem, and even more unlikely since you have an RI. The most common case for seeing this message on an instance type modification is when you try to modify an EC2 Classic instance to an instance family that is VPN Only. Then what the message means is "there is no EC2 Classic instance capacity for the instance type you requested". That said, I've seen one earlier forum post where someone moving from a T2 (VPN Only) to a T3 received the ICE message. In that case AWS confirmed there was plenty of capacity, so something else was going on. I don't know how this was resolved as the resolution was never posted to the forum.

Thank you for the reply, your post gave me a hint.

It turns out that Sydney now has 3 availability zones and t3 rds capacity is only available in 2 of them. I did not have a db subnet in place for the third zone which was added after I set up the original RDS instance. The error message on modifying the instance was vague, but I received a much more detailed error message when I tried to deploy a brand new instance instead.

That's a really interesting resolution, thanks for posting it.