The following is the story of how Randall Degges created a simple API to solve the common problem of external IP address lookup and how he scaled it from zero to over 10 thousand requests per second (30B/month!) using Node.js and Go on Heroku.
Several years ago I created a free web service, ipify. It is a highly scalable IP address lookup service. When you make a GET request against it, it returns your public-facing IP address. Try it out yourself!
I created ipify because, at the time, I was building complex infrastructure...