MongoDB 3.1.5 has been released as a development release, not intended for production use, and will evolve into the 3.2 series for production. This release includes several new fixes and improvements, such as addressing issues with the currentOp command, WiredTiger cache size settings, and the initscript's behavior when stopping a running mongod daemon. Additionally, this release resolves problems with document retrieval speed on WiredTiger versus MMAPv1, and ensures that Mongodump uses the SlaveOk flag by default, among other issues.