after the initial team that designed such document based system have gone to other jobs, once it got harder.

I found my self maintaining and evolving such system need to the changing needs of the business.

I've had to deal with the cases where customer were charged multiple times, some that were never charged at all, and all kind of similar problems.

I can trace almost all of them back to the original decision of lets just ditch a traditional DB for a NoSQL one, because it scales TM and geo redundancy will be easier for our infrastructure team.