I see a lot of requests to my domain that look like this:
"Amazon-Route53-Health-Check-Service (ref <reference ID/ b5996862-d894-4595-88da-7940808e9665>; report http://amzn.to/1vsZADi)"
What are they?
The Health Check service from AWS is performing these requests.
When you associate health checks with an endpoint, Route 53 sends health check requests to the endpoint IP address to validate that they're operating as intended. An issue can occur if an incorrect IP address is specified or if a health check isn't updated or deleted when necessary.
If you need to stop these requests from occurring, then you will need to delete the monitor service from AWS. You can find more details about this process in their documentation:
Route 53 Fix Unwanted Health Checks