Apache Cassandra vs ScyllaDB

Feature comparison

Apache Cassandra is a masterless wide-column store with a fifteen-year production history. The architecture partitions data across nodes via consistent hashing, replicates per-keyspace with tunable consistency, and tolerates regional failure through multi-data-centre topology. Cassandra runs on the JVM, which simplifies operator tooling but introduces garbage-collection considerations at high throughput. Production deployments at Netflix, Apple, Uber, and Discord run thousands of nodes serving petabytes. The project is governed under the Apache Software Foundation with contributions from multiple commercial sponsors including DataStax, Instaclustr, and large user-operators.

ScyllaDB is a Cassandra-compatible database rewritten from scratch in C++ using a shard-per-core architecture built on the Seastar framework. Each CPU core owns a slice of data and a dedicated event loop, eliminating cross-core locking and enabling near-linear scaling with CPU count. ScyllaDB ships its own custom memory allocator, IO scheduler, and userspace TCP. The result is materially higher throughput per node and lower tail latency at high load. Wire compatibility with Cassandra means existing CQL drivers and applications connect without modification.

Both systems share the wide-column data model: partition key plus clustering columns, secondary indexes available but performance-sensitive, and tunable per-query consistency from ONE to ALL. Both lack native multi-row ACID transactions; both provide lightweight transactions through Paxos with significant performance cost. ScyllaDB additionally provides an Alternator API offering DynamoDB-compatible operations, allowing applications written for DynamoDB to migrate without code changes.

Operationally, ScyllaDB streamlines several pain points of self-managed Cassandra. Compaction is more efficient through ScyllaDB's row-based storage; repair is faster through Raft-based metadata coordination introduced in recent versions; and the shard-per-core architecture often requires fewer nodes for the same workload, reducing operational surface area. Cassandra has closed gaps with recent releases — including transactional schema and metadata through Accord and Raft work — but ScyllaDB retained a performance advantage as of 2026.

The strategic differentiator is community and governance. Cassandra is an Apache project with contributions from multiple parties and several commercial alternatives. ScyllaDB is a single-vendor open-core project; the source-available licence and dependence on ScyllaDB Inc for production support introduces concentration risk that some enterprises consider material. ScyllaDB Cloud and Enterprise are well-regarded but the supplier base is narrow.

Pricing comparison

Apache Cassandra itself is free under the Apache 2.0 licence. DataStax Enterprise lists at approximately $5,000–$15,000 per node per year depending on support tier. DataStax Astra DB prices by read/write units and storage similar to DynamoDB. Amazon Keyspaces prices nearly identically to DynamoDB on-demand. ScyllaDB Open Source is source-available under the Source Available Licence (SAL); ScyllaDB Enterprise lists at approximately $3,500–$12,000 per node per year. ScyllaDB Cloud prices by cluster size with managed offerings on AWS and Google Cloud typically running $2,000–$30,000 per month for production clusters.

Five-year cost of ownership for a 100,000 write-per-second steady workload typically lands $2M–$5M for self-managed Cassandra including staffing, $3M–$7M for DataStax Enterprise, $1.5M–$4M for self-managed ScyllaDB (smaller fleet for the same workload), and $2M–$6M for ScyllaDB Cloud. The primary buying-side caveat for ScyllaDB is single-vendor risk: while the wire protocol is Cassandra-compatible, escape from ScyllaDB-specific tuning and operational patterns requires effort if commercial support ever becomes untenable. For Cassandra, the caveat remains staffing intensity — production self-managed Cassandra demands specialist expertise that is increasingly scarce. Pricing as of May 2026.

When to choose Apache Cassandra

Choose Apache Cassandra when community breadth, multi-vendor commercial support, and governance through the Apache Software Foundation matter more than raw throughput per node, when existing operational tooling and runbooks are built around Cassandra, when the organisation has Cassandra expertise on staff, or when procurement requires vendor-neutral open-source software. Cassandra suits very large existing deployments where migration risk outweighs efficiency gain, regulated industries with strict open-source provenance requirements, and organisations with multiple commercial support relationships.

When to choose ScyllaDB

Choose ScyllaDB when throughput per node matters for infrastructure cost, when P99 latency under high load is a hard requirement, when the workload is large enough that node count reduction translates to material spend savings, when the team is willing to depend on a single commercial sponsor, or when DynamoDB-compatible workloads need a portable home through the Alternator API. ScyllaDB suits ad-tech, IoT ingestion, telemetry, and gaming workloads with predictable hotspots where per-node efficiency drives architecture economics.

Alternatives to both