Ahrefs

Ahrefs owns the whole pipeline behind its data, from crawling the open web to storing and serving it. That index lives on a custom distributed key-value store holding roughly 25 petabytes of live data, and the backend that runs it is written mostly in OCaml and C++, with a ReasonML frontend. In 2022 the company went further and built Yep, its own independent search engine, so it would not have to lean on Google or Bing APIs to understand how the web is searched.

The engineering culture is flat and lean: teams stay small, autonomy is high, and there is no dedicated product manager role, so designers own product and design together. The company motto, "First do it, then do it right, then do it better," captures a bias toward shipping and iterating over heavy upfront planning. That same pragmatism runs through the stack: Ahrefs relies heavily on open-source code, contributes back, and publishes its engineering work on a public tech blog.