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Databases · Updated 2026-06-06

Cassandra vs Scylla

ScyllaDB is a ground-up C++ reimplementation of Cassandra that keeps CQL and the data model but replaces the JVM with a shard-per-core, thread-per-core architecture — usually delivering lower and more predictable tail latency on fewer, denser nodes. Cassandra is the mature original with the widest community, broadest ecosystem, and the safety of the Apache Foundation. Choose Scylla for raw per-node performance and tighter latency SLAs; choose Cassandra for ecosystem maturity and vendor-neutral governance.

Apache Cassandra
The original masterless wide-column store.
Since
2008
By
Apache Software Foundation
License
Apache-2.0
cassandra.apache.org ↗
ScyllaDB
A C++ rewrite of Cassandra with a shard-per-core engine.
Since
2015
By
ScyllaDB, Inc.
License
Source-available (AGPL history; see project)
www.scylladb.com ↗

Same CQL, same masterless ring, same Dynamo-style replication — different engine underneath. Scylla’s C++ shard-per-core design squeezes more throughput per node and tighter tails; Cassandra brings the larger community and the assurance of foundation governance. Scylla is largely drop-in compatible, which makes it a common performance-driven migration target.

Quick takes

If you're…

  • You need the lowest, most predictable tail latency Scylla Shard-per-core avoids JVM GC pauses and contention.
  • You want to run on fewer, denser nodes Scylla Scylla typically achieves more throughput per node.
  • You value Apache Foundation governance and neutrality Cassandra Cassandra is vendor-neutral under the ASF.
  • You rely on the broadest community and tooling Cassandra Cassandra’s ecosystem and operational lore are larger.
  • You are migrating an existing Cassandra workload for speed Scylla Scylla is largely CQL-compatible; migrations are common.
Decision wizard

A few questions, a verdict.

Q1

What matters most?

Q2

How sensitive are you to GC pauses?

Q3

Greenfield or migration?

At a glance

The scorecard.

Dimension
Cassandra
Scylla
Edge
Engine core
JVM
C++ shard-per-core
Scylla
Tail latency core
GC-sensitive tails
Tight, predictable tails
Scylla
Compatibility features
Reference CQL
Drop-in CQL
tie
Node density ops
More nodes
Denser nodes
Scylla
Governance ecosystem
ASF, neutral
Vendor-led
Cassandra
Ecosystem & community ecosystem
Largest
Growing
Cassandra
In depth

Dimension by dimension.

core

Engine

edge: Scylla
Cassandra

JVM-based; subject to GC tuning.

Scylla

C++ with a shard-per-core, thread-per-core design (Seastar).

core

Tail latency

edge: Scylla
Cassandra

Good, but GC can cause spikes under load.

Scylla

Lower and more predictable p99 by design.

features

Compatibility

tie
Cassandra

The reference CQL implementation.

Scylla

CQL + much of the wire protocol; largely drop-in.

ops

Node density

edge: Scylla
Cassandra

More nodes for the same throughput.

Scylla

More throughput per node; fewer machines.

ecosystem

Governance

edge: Cassandra
Cassandra

Apache Foundation, vendor-neutral.

Scylla

Single-vendor, source-available licensing.

ecosystem

Ecosystem & community

edge: Cassandra
Cassandra

Largest community, drivers, and operational knowledge.

Scylla

Growing; benefits from CQL compatibility.

When to pick neither

A different shape of problem.

  • DynamoDB
    You want a fully-managed wide-column/KV store on AWS
  • Astra DB
    You want managed Cassandra without running it yourself
  • CockroachDB
    You need distributed SQL with strong consistency
Situational picks

For specific cases.

Latency-critical workload with strict p99 SLAs

Scylla

Shard-per-core avoids GC jitter and tightens tails.

Cost-driven consolidation onto fewer machines

Scylla

Higher per-node throughput reduces the fleet size.

A team that prizes vendor neutrality

Cassandra

Apache governance avoids single-vendor licensing risk.

Maximum community support and hiring pool

Cassandra

Cassandra’s ecosystem and talent pool are the largest.

Sources

Primary material.

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