CarrotDB is Redis (www.redis.io) - compatible in memory data type store, which provides better memory utilization (5x times on average), easy way to enhance its functionality via custom co-processors, filters, aggregations and functions (stored procedures).
The maximum size of a regular key and value is limited by Short.MAX_VALUE and maximum block size, which is on a low end (4-8KB). Add support for large k-v's. They will be allocated outside of a block.