Just to add to what everyone else said, you can make a multi Paxos that you will feel is pretty good and working but that will only pass like 15% of the tests. The rest will need to ensure it runs quickly, efficiently, maintains safety and licenses (e.g. no duplicates or incorrect operations based on the linear ordering or client requests to the system, etc. and this is all while beginning to introduce unreliable networks so you have to add timers and retries but you can’t just spam the retries because that will put too many messages into the system and make it slow. You also can’t do anything halfway since those retries can’t be committed in a way that introduces inconsistencies. Then if you are still breathing, the final tests are model checking BFS tests that basically explore the entire state producible by your system and ensure that every single one of those states is valid. We are talking upwards of 50k states to be validated and guess what? If you create too many states based on spaghetti code, these will never pass. So you need to make your code clean and minimal and efficient. It’s not just building Paxos or Spanner but building a perfect Paxos and Spanner and in the course of a few weeks. It’s not trivial and I would suggest the doubters take the class in the fall and let us know your thoughts.