Cassandra vs ScyllaDB vs DynamoDB: Wide-Column Stores Compared

If you need wide-column at scale, you have three viable options. The right pick depends on your operational stomach.

Cassandra: the OG

Cassandra: open-source; mature; tunable consistency; needs careful operation.

Best when you have Cassandra-experienced engineers and a budget for the ops tier.

ScyllaDB: same data model, faster

• ScyllaDB: C++ rewrite; same Cassandra API; significantly faster and lower-resource.
• Best when you outgrew Cassandra performance but want the same data model.

DynamoDB: managed-only path

DynamoDB: AWS-managed; provisioned or on-demand; auto-scales; locked to AWS.

Best when you want to skip the ops entirely and you are AWS-committed.

Cost and ops compared

Cost @ 100K writes/sec: Cassandra ~$5k/mo (self-managed); ScyllaDB ~$3k/mo; DynamoDB on-demand ~$15k/mo, provisioned ~$8k/mo.

Ops cost: Cassandra/Scylla need engineers; DynamoDB does not.

Antipatterns

• Cassandra without operational maturity. Outage time exceeds savings.
• DynamoDB with poor key design. Hot partitions; cost explodes.
• Migrating between them every 18 months. Data has gravity.

What to do this week

Three moves. (1) Run a 30-day trial of the candidate against your real workload. (2) Compare TCO + workflow fit, not just feature checklists. (3) Decide and commit; running both in parallel is the most expensive option.