Did anyone here ever see a migration _from_ PostgreSQL/MySQL _to_ MongoDB? I've only ever seen startups pick Mongo, then regret it a few months or years down the line and migrate to a relational database. Did anyone ever see the opposite?
It's just far more common for some tech lead in small company to imagine that they are going to be bigger than Netflix, than for someone to start conservatively with a RDBMS, and realize that suddenly they have hundreds of millions of users and some kinds of data where the relational bits don't matter.
It didn't seem like it made things better since there were issues with dates and lost data. Working with it now isn't fun either.
I will say in case anyone doesn't understand how this might be possible, relational querying is possible in document databases, but they essentially require just different ideas to achieve. In Dynamo, you might need to create secondary indices for example.
Personally I love Postgres and would not mind if we had gone that direction but the more I use DynamoDB the less I feel like Postgres is the "only way"