Two implementations of state backends are available:

RocksDB⌗

An embedded key/value store keeps its working state on disk.

Overhead⌗

Accesses and updates involve serialization and deserialization.

Java heap-based state backend⌗

Keeps its working state in memory, on the Java heap.

Risk⌗

Large amount state will cause OOM.

Conclusion⌗

Both of these state backends are able to do asynchronous snapshotting, meaning that they can take a snapshot without impeding the ongoing stream processing.