Nearly everything that is passed around inside Google is represented using Protocol Buffers. There are no internal REST APIs, and there’s no JSON or XML. Instead, the services and microservices used inside Google receives and sends protocol buffers, and it’s been estimated that across all Google data centers, over ten billion API calls are made every second. That volume of usage is why protocol buffers are used, and it’s why the Protocol Buffer encoding has been optimized for fast writing and reading.
You might be surprised to learn that there are virtually no REST APIs used inside Google. That’s right, the vast majority of Google’s internal microservices don’t use REST. Instead, almost everything communicates using gRPC or a precursor of gRPC called “Stubby.”
As an industry, we’re beholden to test methodologies invented in an era vastly different to the current one we’re in. People still seem to be enamored with ideas such as full test coverage (so much so that at certain companies a merge is blocked if a patch or a new feature branch ends up fractionally decreasing the test coverage of the codebase), test-driven development and complete end-to-end testing at the system level.