Cassandra 5.0 is Officially Released

On September 5, the Cassandra 5 GA release was announced. Why is it important? First, Cassandra doesn't get updated very often; the last major release was in 2021. Second, the end-of-support for the 3.x series was announced at the same time. So, if you're still using 3.x, it's time to start planning an upgrade at least to 4.x.

Key changes:
- Storage Attached Indexes (SAI) (CEP-7). This is a new index implementation that replaces Cassandra secondary indexes, fixing their limitations. It allows creating indexes for multiple columns on the same table, improves query performance, reduces index storage overhead, and support complex queries (like numeric range, boolean queries).
- Trie Memtables and Trie SSTables (CEP-19, CEP-25). This is a change of the underlying data structures for the in-memory memtables and on-disk SSTables. These storage formats utilize tries and byte-comparable representations of database keys to improve Cassandra’s performance for reads and modification operations.
- Migration to JDK 17
- Unified Compaction Strategy (UCS) (CEP-26). It combines the tiered and levelled compaction strategies into a single algorithm. UCS has been designed to maximize the speed of compactions, using a unique sharding mechanism that compacts partitioned data in parallel.
- New Aggregation and Math Functions. Cassandra 5 adds new native CQL functions like count, max, min, sum, avg, exp, log, round and others. Users can also create their own custom functions.
- Approximate Nearest Neighbor Vector Search (CEP-30). The feature uses SAI and a new Vector CQL type. Vector is an array of floating-point numbers that show how similar specific objects or entities are to one another. It is a powerful technique for finding relevant content within large document collections and it can be used as a data-layer technology for AI/ML projects.

New Cassandra release makes significant optimizations in existing functionality and brings some really promising new features. For full details, you can check out the release notes here.

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