Not necessarily, and not in the very common single-writer-many-reader case. In that case, PostreSQL's MVCC allows all readers to see consistent snapshots of the data without blocking each other or the writer. TTBOMK, any other mechanism providing this guarantee requires locking (making deadlocks possible).
So: Does Mongo now also implement MVCC? (Last time I checked, it didn't.) If not, how does it guarantee that reads see consistent snapshots without blocking a writer?
Not necessarily, and not in the very common single-writer-many-reader case. In that case, PostreSQL's MVCC allows all readers to see consistent snapshots of the data without blocking each other or the writer. TTBOMK, any other mechanism providing this guarantee requires locking (making deadlocks possible).
So: Does Mongo now also implement MVCC? (Last time I checked, it didn't.) If not, how does it guarantee that reads see consistent snapshots without blocking a writer?