Concurrency Internals in MongoDB v2.2

“10gen CEO & Co-Founder Dwight Merriman will look “under the hood” atconcurrency internals in the upcoming version of MongoDB…”

“The Aggregation Framework is available in its first production-ready release as of 2.2. The aggregation framework makes it easier to manipulate and process documents inside of MongoDB, without needing to use Map Reduce, or separate application processes for data manipulation…”

“v2.2 eliminates the global lock in the mongod process.  Locking is now per database.  In addition a new subsystem avoids locks under most page-fault events; thus concurrency improves even on systems with a single database.   Parallelism in application of writes on secondaries is enhanced also…”