Aurora serverless v2 minimum subnet size

Question

Are there any constraints regarding the size of private subnets for Aurora serverless v2 nodes? I've tested a scenario with /28 subnets, which seems to work without any problems, but I'd like to make sure I'm not missing something important.

[From the documentation:](https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/USER_VPC.WorkingWithRDSInstanceinaVPC.html)
> The CIDR blocks in each of your subnets must be large enough to accommodate spare IP addresses for Amazon Aurora to use during maintenance activities, including failover and compute scaling. For example, a range such as 10.0.0.0/24 and 10.0.1.0/24 is typically large enough.

A /24 for a single node per AZ seems to be rather wasteful IMHO.

AWS-User-0357409 · Accepted Answer

Hi,
This really comes down to the size and use case.  The best way to think about it is that Aurora Serverless v2 consume network resources just like a provisioned DB instance (1 ENI and 1 IP from your DB subnet group).  So, to answer your question, a /28 would work but you need to plan for scale.

I agree that one node and a /24 would be perceived as wasteful, but make sure to consider what your future state may look like and if that /28 is appropriate.

Aurora serverless v2 minimum subnet size

Relevant content