Question on Aurora Postgres

Hello.

I think it would be a good idea to refer to the text in the following document for a guideline for instance types.
For small workloads other than production environments, I think it is better to use the T-based instance class.
In a production environment, it depends on how the application uses the database, but in general, R-based memory-optimized instance classes are often used.
https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/Concepts.DBInstanceClass.html

For Dev/Qa/Uat type environments I would look at using Aurora Serverless V2 (if your AWS region supports it) and see how you go. If those environments are not used 24x7 then this is likely to save you money. Start with a smaller amount of ACUs and scale up.

Each ACU is a combination of approximately 2 gibibytes (GiB) of memory, corresponding CPU, and networking. You specify the database capacity range using this unit of measure

This page covers some guidelines around capacity for Aurora Serverless.

For Perf/Prod look at the metrics that comes out of RDS in terms of memory/CPU from there work out if you want to go down the memory optimized (R Instance Types) or compute optimised (C instance Types) instance paths. If neither seems to be the constrained consider using an multi-purpose instance type (M). You can consider Serverless for Production as well however the AWS documentation states

This type of automation is especially valuable for multitenant databases, distributed databases, development and test systems, and other environments with highly variable and unpredictable workloads.

Using Aurora Serverless is not a one-way door as you can move back to standard instance types if you want