The key Sleepycat people went on to write WiredTiger which was acquired by Mongo -- it has some interesting features: <a href="http:&#x2F;&#x2F;source.wiredtiger.com&#x2F;2.6.1&#x2F;index.html" rel="nofollow">http:&#x2F;&#x2F;source.wiredtiger.com&#x2F;2.6.1&#x2F;index.html</a><p>&gt; WiredTiger supports row-oriented storage (where all columns of a row are stored together), column-oriented storage (where columns are stored in groups, allowing for more efficient access and storage of column subsets) and log-structured merge trees (LSM), for sustained throughput under random insert workloads.<p>&gt; WiredTiger includes ACID transactions with standard isolation levels and durability at both checkpoint and fine-grained granularity.<p>&gt; WiredTiger can be used as a simple key&#x2F;value store, but also has a complete schema layer, including indices and projections.