I'm usually against absolutes, but I'm really in agreement here. It's almost always better to use a relational database, and in the rare cases where you wouldn't want a relational database, MongoDB is the worst of the major options. It literally memory leaks and drops data without warning or provocation. If you're not going to go with a relational database, RethinkDB, Cassandra, Redis, or BerkeleyDB would all be better choices (which one depends on situation).