Version 2

• Background index creation (since v.1.4)
• Sharding (since v.1.6)
• More query operators (since v.1.6)
• Journaling (since v.1.8)
• Sparse and covered indexes (since v.1.8)
• Compact command to reduce disk usage
• Memory usage more efficient
• Concurrency improvements
• Index performance enhancements
• Replica sets are now more configurable and data center aware
• MapReduce improvements
• Authentication (since 2.0 for sharding and most database commands)
• Geospatial features introduced