I\'m new to API Gateway, and as far I have tried is a really powerful tool. For the project I\'m working right now we are using a PostgreSQL instance in RDS. I\'ve seen that is
No this isn't possible. The API Gateway service proxy will only proxy calls to the AWS API. The RDS API only allows you to do things like create a database, delete a database, take snapshots, etc. It doesn't allow you to connect and run queries against the database.
You should look into pointing API Gateway at a Lambda function that has the ability to connect to your RDS database and run queries.