https://docs.mongodb.com/manual/reference/command/getMore/

The documentation specifies: "If you do not specify a value for maxTimeMS, operations will not time out. A value of 0 explicitly specifies the default unbounded behavior."

It would appear that this is not the case for some cursor types. For instance, a tailable + awaitData cursor on a capped collection (oplog), will default `maxTimeMS` to 1 if the user omits the key. I'm not sure about other special cases, but it seems like we can at least document this one? Here is the ticket related to that detail: SERVER-19665