Cheapest way to run Flyway on AWS

I'm looking for a way to run Flyway for my Database schemas with AWS. My RDS is in private subnet. I'm looking for the cheapest way to do this.

1. Database schema should be pulled from github.
2. Flyway must be installed
3. Schema must be migrated

I can do this using Codebuild, but NAT is required to pull the code from Github and install Flyway. Is there a cheaper way to do this?

Here are some options I'm considering:

• NAT will be created when codebuild runs, NAT will be deleted when it finishes
• Flyway and Schema migration scripts will be transmitted externally to codebuild. (I don't know if there is a way to do this. Docker for example?)
• Can I do something using Gateway Endpoint for s3?