Ever wish you could dynamically route requests to APIGateway Custom Domains based on headers, not just the host name?

Oddly enough I have but I am an AWS super nerd like that. They released advanced Routing Rules you can set that will take into account headers like cookies before proxying the traffic through.

What are the use cases for it?

A/B testing and blue green deployments come to mind. In my new eBook the CTOs guide to AI/ML on AWS I have an entire bonus section about how to roll out AI features and A/B test them and this is a dream for me.

Lets say you had a feature you wanted 10% of your customers to have access to, you could have 2 running versions of your application going. The old one running on cluster A and the new one running on cluster B.

When a user first visits your site you would segment them into groups by giving them a header that would be passed in with each request.

By default the your users would flow towards Cluster A but if they were in that 10% you wanted to test the new feature set on they would get sent to Cluster B to experience the new functionality.

If you need to do an emergency roll back just change the rules to send everyone back to cluster A and within a few seconds cluster B will be invisible to the entire web.

Admittedly this isn’t as groundbreaking and the MCP stuff I have been working on but still nice to have.

Questions for you:

What other use cases can you think of for this functionality?

What are your biggest API Gateway headaches?