Local in-memory off heap JVM key-value store

Question

I am looking for a JVM library implementing ConcurrentHashMap to store large map in local memory. Expected to have 20,000,000 items in this map with overall size of 2-3 Gb. No need to distribute data set across hosts.

Load mostly reads with a few writes. Infrequient writes are snapshot updates when whole map content should be replaced with new data.

Would prefer a library with a minimum of dependencies to simplify integration. Would be nice to re-package the library with jarjar for re-distirbution inside my own package.

So far I encountered * ChronicleMap * Apache Ignite * Hazelcast

Could you please recommend which one of those fit my use case better?

Answer 1

Hazelcast

For your problem I recommend hazelcast.

ReplicatedMap

• Made for extensive read operations.
• Allow you to write custom serialization and deserialization classes which decrease CPU cost while reading and writing.

Sql-Support

• Allow you to run SQL query on top of your map.

• Allow you to make indexes on map variables which makes custom retrieval so fast.

Build

• Only a single jar is enough to make hazelcast environment.

Answer 2

MapDb appears to be what you're looking for.