I'm mostly guessing based on what I've read over the years. They've published a hefty corpus of work regarding their deployment infrastructure and greater code

I'm mostly guessing based on what I've read over the years. They've published a hefty corpus of work regarding their deployment infrastructure and greater code review/quality approach. Here's a few examples: - https://code.fb.com/web/rapid-release-at-massive-scale/ https://code.fb.com/web/rapid-release-at-massive-scale/. - https://www.quora.com/How-does-Facebook-release-deploy-process-work-What-tools-and-processes-does-Facebook-use-to-push-changes-to-the-site# https://www.quora.com/How-does-Facebook-release-deploy-proce...