https://youtube.com/watch?v=HV_MiVo30Jg
This walks through how to set up an API key on AWS API Gateway. API keys on AWS API Gateway go in tandem with Usage plans. Because of that, I also walk through setting up a Usage plan.
This all combos with an AWS Lambda function that is called from the AWS API Gateway.
I am using this on AWS in order to create an API that allows you get business details from Secretary of States around the country.