[lwat]

> When you have so many writes that sharding isn't enough.

Does Mongo still have a global write lock?

[elchief]

no longer (but only a few months)

[mgummelt]

Though I believe it still has a per-collection lock.

[Jare]

It has per-database locking. Per-collection is being worked on but no planned date yet. [1]

[1] http://www.mongodb.org/display/DOCS/How+does+concurrency+wor...