Mongo does have a global write lock. A per-db lock does me very little good when I only have one DB. As to your linked doc, emphasis added: > In some situatio

Mongo does have a global write lock. A per-db lock does me very little good when I only have one DB. As to your linked doc, emphasis added: > In some situations, read and write operations can yield their locks. > Long running read and write operations, such as queries, updates, and deletes, yield under many conditions. In practice, I've been bitten hard by this. A new feature rolls out, and users can't log in anymore, because a query is taking 2 minutes to run.