title: Understanding the health check and multi region implementation of API Gateway
body: <p>I'm trying to implement a health check for multiple API Gateways deployed to multiple regions. For this, I'm following <a href="https://aws.amazon.com/blogs/compute/building-a-multi-region-serverless-application-with-amazon-api-gateway-and-aws-lambda/" rel="nofollow noreferrer">this article</a>.</p>
  <p>Long story short, you need to replicate the exact same API Gateways (and their corresponding Lambda functions) in all of the regions. The use Route53 to create one domain name backed by multiple endpoints.</p>
  <p>My question is related to the way Route53's set up. In that article, health check endpoints are populated by API Gateway's <em>Stage Invoke URLs</em>. While region endpoints are populated by <em>Target Domain Name</em> from API Gateway's Custom Domain Name.</p>
  <p>Why are these two endpoints populated by different values? If we can use <em>Stage Invoke URL</em> in the health check, why do we need to have <em>Custom Domain Name</em> in the first place? Why can't we just use the same <em>Stage Invoke URL</em> to populate the region endpoints?</p>