Scylla Java Driver for Scylla and Apache Cassandra®¶

Deprecation Notice: Scylla Java Driver 3.x is now deprecated and has entered maintenance mode. Only critical bug fixes will be accepted. For new projects and active development, please migrate to Scylla Java Driver 4.x (documentation).

If you’re reading this on github.com, please note that this is the readme for the development version and that some features described here might not yet have been released. You can find the documentation for the latest version through the Java driver docs or via the release tags, e.g. 3.11.5.20.

A modern, feature-rich and highly tunable Java client library for Apache Cassandra (2.1+) and using exclusively Cassandra’s binary protocol and Cassandra Query Language v3.

The Scylla Java Driver is a fork from DataStax Java Driver, including some non-breaking changes for Scylla optimization, with more updates planned.

Features:

• Like all Scylla Drivers, the Scylla Java Driver is Shard Aware and contains extensions for a tokenAwareHostPolicy. Using this policy, the driver can select a connection to a particular shard based on the shard’s token. As a result, latency is significantly reduced because there is no need to pass data between the shards.

• Lightweight Transaction (LWT) Optimization:

  • When using TokenAwarePolicy with prepared statements, LWT queries automatically use replica-only routing, prioritizing local datacenter replicas to minimize coordinator forwarding overhead and reduce contention during Paxos consensus phases.

  • When using RackAwareRoundRobinPolicy, LWT queries skip local rack prioritization and distribute evenly across all hosts in the local datacenter. This avoids creating rack-level hotspots during Paxos consensus, which can lead to increased contention and reduced throughput. The local datacenter is still prioritized over remote datacenters to maintain low latency.

  • When using LatencyAwarePolicy, LWT queries bypass latency-based reordering to preserve deterministic replica selection. This ensures that LWT routing assumptions (such as consistent coordinator selection for optimal Paxos performance) are maintained throughout the policy chain.

• Sync and Async API

• Simple, Prepared, and Batch statements

• Asynchronous IO, parallel execution, request pipelining

• Connection pooling

• Auto node discovery

• Automatic reconnection

• Configurable load balancing and retry policies

• Works with any cluster size

• Query builder

• Object mapper

The driver architecture is based on layers. At the bottom lies the driver core. This core handles everything related to the connections to a Cassandra cluster (for example, connection pool, discovering new nodes, etc.) and exposes a simple, relatively low-level API on top of which higher level layers can be built.

The driver contains the following modules:

• driver-core: the core layer.

• driver-mapping: the object mapper.

• driver-extras: optional features for the Java driver.

• driver-examples: example applications using the other modules which are only meant for demonstration purposes.

• driver-tests: tests for the java-driver.

Useful links:

• SCYLLA UNIVERSITY JAVA CLASS

• DOCS: the manual has quick start material and technical details about the driver and its features.

• GITHUB REPOSITORY: https://github.com/scylladb/java-driver

• changelog

<dependency>
  <groupId>com.scylladb</groupId>
  <artifactId>scylla-driver-core</artifactId>
  <version>3.11.5.20</version>
</dependency>

<dependency>
  <groupId>com.scylladb</groupId>
  <artifactId>scylla-driver-mapping</artifactId>
  <version>3.11.5.20</version>
</dependency>

<dependency>
  <groupId>com.scylladb</groupId>
  <artifactId>scylla-driver-extras</artifactId>
  <version>3.11.5.20</version>
</dependency>