They still use it for anything that runs on the application layer, i.e. stuff the runs in-process on the machines that serve web and GrahphQL API requests. FB

They still use it for anything that runs on the application layer, i.e. stuff the runs in-process on the machines that serve web and GrahphQL API requests. FB isn’t as steeped in modern service-oriented ideology as most similar companies, so that `www` monorepo represents a lot more code than you probably expect, including stuff you’d normally think of as “services”. True backend services do exist outside the PHP application, and are typically written in C++. Java, Rust, and Python also exist in various niches. The only mainstream language I have never seen anywhere at FB is Go, although I’m sure any language you can imagine is used by _some_ random team out there. I’m not sure why Hack would be unpopular. On the contrary, it’s the default choice for starting new projects since all of the internal tooling is built mostly with Hack in mind, so it’s the path of least resistance for developers.