Hyperscaling Have I Been Pwned with Cloudflare Workers and Caching

Summary

I've spent more than a decade now writing about how to make Have I Been Pwned (HIBP) fast. Really fast. Fast to the extent that sometimes, it was even too fast:The response from each search was coming back so quickly that the user wasn’t sure if it was legitimately checking subsequent addresses they entered or if there was a glitch.Over the years, the service has evolved to use emerging new techniques to not just make things fast, but make them scale more under load, increase availability and sometimes, even drive down cost. For example, 8 years ago now I started rolling the most important services to Azure Functions, "serverless" code that was no longer bound by logical machines and would just scale out to whatever volume of requests was thrown at it. And just last year, I turned on Cloudflare cache reserve to ensure that all cachable objects remained cached, even under conditions where they previously would have been evicted.And now, the pièce de résistance, the coolest performance thing we've done to date (and it is now "we", thank you Stefán): just caching the whole lot at Cloudflare. Everything. Every search you do... almost. Let me explain, firstly by way of some background:When you hit any of the services on HIBP, the first place the traffic goes from your browser is to one of Cloudflare's 330 "edge nodes":As I sit here writing this on the Gold Coast on Australia's most eastern seaboard, any request I make to HIBP hits that edge node on the far right of the Aussie continent which is just up the road in Brisbane. The capital city of our great state of Queensland is just a short jet ski away, about 80km as the crow flies. Before now, every single time I searched HIBP from home, my request bytes would travel up the wire to Brisbane and then take a giant 12,000km trip to Seattle where the Azure Function in the West US Azure data would query the database before sending the response 12,000km back west to Cloudflare's edge node, then the final 80km down to my Surfer...