• Indexes: Mongod now recognizes incompatible “future” text and geo index versions and exits gracefully (SERVER-12914$^{699}$) 

• Indexes: Fixed issue that can cause secondaries to fail replication when building the same index multiple times concurrently (SERVER-12662$^{700}$) 

• Indexes: Fixed issue that can cause index corruption on the tenth index in a collection if the index build fails (SERVER-12481$^{701}$) 

• Indexes: Introduced versioning for text and geo indexes to ensure backwards compatibility (SERVER-12175$^{702}$) 

• Indexes: Disallowed building indexes on the system.indexes collection, which can lead to initial sync failure on secondaries (SERVER-10231$^{703}$) 

• Sharding: Avoid frequent immediate balancer retries when config servers are out of sync (SERVER-12908$^{704}$) 

• Sharding: Add indexes to locks collection on config servers to avoid long queries in case of large numbers of collections (SERVER-12548$^{705}$) 

• Sharding: Fixed issue that can corrupt the config metadata cache when sharding collections concurrently (SERVER-12515$^{706}$) 

• Sharding: Don’t move chunks created on collections with a hashed shard key if the collection already contains data (SERVER-9259$^{707}$) 

• Replication: Fixed issue where node appears to be down in a replica set during a compact operation (SERVER- 12264$^{708}$) 

• Replication: Fixed issue that could cause delays in elections when a node is not vetoing an election (SERVER- 12170$^{709}$) 

• Replication: Step down all primaries if multiple primaries are detected in replica set to ensure correct election result (SERVER-10793$^{710}$) 

• Replication: Upon clock skew detection, secondaries will switch to sync directly from the primary to avoid sync cycles (SERVER-8375$^{711}$) 

• Runtime: The SIGXCPU signal is now caught and mongod writes a log message and exits gracefully (SERVER- 12034$^{712}$) 

• Runtime: Fixed issue where mongod fails to start on Linux when /sys/dev/block directory is not readable (SERVER-9248$^{713}$) 

• Windows: No longer zero-fill newly allocated files on systems other than Windows 7 or Windows Server 2008 R2 (SERVER-8480$^{714}$) 

