I've also used MongoDB in production, processing millions of new records per month, but the systems requirements to handle that load outstrip PostgreSQL by a ma

I've also used MongoDB in production, processing millions of new records per month, but the systems requirements to handle that load outstrip PostgreSQL by a magnitude of 10x. Also, the various gotchas involved with maintaining MongoDB at scale meant I spent most of my team's time chasing down esoteric problems instead of serving customers. But ultimately, trusting a database with decades of development behind it to handle something like a JOIN turns out to be a good idea. In my experience.