"I am sure the app you wrote does not have millions of users daily, either" This argument is weak. Its not like millions of people are crammed within the app a

"I am sure the app you wrote does not have millions of users daily, either" This argument is weak. Its not like millions of people are crammed within the app all at the same time, while integrated with AD, or other microsoft bloatware. It may impress inexperienced devs, but it's really not much of an architectural challenge. MS could have done a better job. But to satisfy your curiosity, my background is in developing some rather large systems, used by hundreds of millions. Not these apps specifically (although they do handle large amounts of data, a lot more than teams), and it's a good indicator that I know what I am talking about and without bragging I can smell poor design and a lazy job.