I had a quick look and.. I have no idea. Frontend development at meta works differently than you probably imagine: things aren’t built locally but on dev servers or on-demand instances that all run services that take care of any build jobs in the background. I don’t know if there’s any nodejs involved at any point there or later in CI, but I suppose it’s possible. I still think it’s unlikely because my search turned up barely any mentions of nodejs, so I still think that my main point holds true: there’s very little node in use at meta, and nearly all the facebook frontend services are php (or python for Instagram/threads)