I wonder what this ultimately cost. Migrating from a document model to a relational DB requires code change in pretty much every single location it’s used. That’s a lot of engineer time to develop, test, and do the data migration.
Clearly you don't.
They did have the correct understanding/skills to manage a Mongo DB, and on top of that they bough the MongoDB-Inc-recommended management tools and the MongoDB-Inc-recommended support plan.
Basically they were doing everything by the book, as advertised and advised by MongoDB itself.
Yet they were having problems, so much so that even MongoDB Inc's own support engineers weren't able to help.
After a great lenght of discomfort they evaluated that MongoDB was not a good fit for them, and moved to PostgreSQL.
According to the post they paid Mongo a lot of money for support and they didn’t have the correct understanding/skills either.
It sounds to me like the core problem is their requirement to run Mongo on their own AWS stack rather than Mongo’s, and while Mongo claimed to support it seems like they didn’t really.
No doubt this was a huge migration but from my personal perspective going from Mongo to Postgres feels like a move in the right direction in the long term. For one you have a lot more options for support!
It is reasonably straightforward to deal with relational databases in comparison, this is a well-known space.
> That’s a lot of engineer time to develop, test, and do the data migration.
Downtime is more expensive.
EDIT: Also, the article says that they spent at least two months a year planning and executiting database upgrades, since the OpsManager tool from MongoDB Inc wasn't able to help.