The write lock does matter. We at 10gen won't say otherwise. A good amount of work in the current and upcoming releases are adding more granularity to the write

The write lock does matter. We at 10gen won't say otherwise. A good amount of work in the current and upcoming releases are adding more granularity to the write lock. See current progress in jira https://jira.mongodb.org/browse/SERVER/component/10055 https://jira.mongodb.org/browse/SERVER/component/10055 That said, as that blog post clearly demonstrates, the write lock is a red herring in a vast majority of circumstances. In practice it is historically rarely been an issue and even less so with the yielding improvements in 2.0 (which is what that blog post is about). Typically issues are manifested in lack of adequate ram, lack of IO and poor schema design.