[SergeAx]

I was reading your reply too quick, sorry. Anyway, even failover replication in PG is not there out of the box and have it's quirks.

[mst]

I don't disagree at all with that statement although invetably what mongo does have out of the box definitely has its own quirks.

Getting operations right is tricky no matter what you're doing/using, and you always have to learn your backend's idiosyncracies no matter which one you choose.