cache2k vs Garnet

cache2k is an Apache-licensed, open-source library that keeps Java application objects in memory. Its project describes a JAR smaller than 400 KB with no external dependencies, and the implementation is written in pure Java without sun.misc.Unsafe. Cache behavior includes automatic expiry, refresh, refresh ahead, read-through loading, and event listeners. Cache loaders can suppress exceptions or retry them according to configuration. Integrations listed include Spring Framework, Scala Cache, DataNucleus through JCache, and Hibernate through JCache. cache2k supports JCache / JSR 107, while its guide notes extra overhead for that API compared with the native interface. Monitoring options include low-overhead statistics, JMX, and documented Micrometer metrics. Version 2 requires Java 8 or later and is described as compatible with Android API level 26. The library is free, available from Maven Central, self-hosted, and does not persist data.

Garnet is a free remote cache-store from Microsoft Research for self-hosted use on Linux, macOS, and Windows. It uses RESP and works with many unmodified Redis clients, including StackExchange.Redis; documented libraries also include Jedis, Redisson, redis-py, node_redis, and go-redis. Its data APIs cover strings, lists, hashes, sets, sorted sets, geo operations, HyperLogLog, bitmaps, ACLs, pub/sub, transactions, and Lua scripting. Garnet can store datasets larger than memory on local or cloud storage and supports checkpointing and recovery. Multi-node mode provides sharding, state migration, and replication. Developers can register C# data structures and read-modify-write operations through its custom operator framework. TLS/SSL and password-based RESP authentication are supported. DiskANN vector database support and Bf-Tree range indexes are marked preview. Garnet is MIT-licensed, but is not intended as a fully compatible Redis replacement and does not support Redis modules. The self-hosted plan is free; you manage infrastructure, updates, and operations. The managed Azure Cosmos DB Garnet Cache is in expanded Private Preview, with no price listed.