AWS Keyspaces cost: serverless Cassandra billed per request and GB

Quick answer

Amazon Keyspaces (managed Cassandra) bills read and write request units plus storage per GB-month, in either on-demand (pay per request, scales to zero) or provisioned (reserve capacity, cheaper for steady load) mode, with no clusters to run. On-demand suits spiky or unpredictable workloads; provisioned with auto-scaling suits steady traffic. It removes Cassandra operational cost at the price of per-request billing.

Amazon Keyspaces is a serverless, Cassandra-compatible database. It removes the considerable operational cost of running Cassandra yourself, and prices access by request and data by storage, with the same on-demand-versus-provisioned choice as DynamoDB. The mode decision is the main cost lever.

Requests and storage

Dimension	Bills for
Reads	Read request units (by consistency and size)
Writes	Write request units (by size)
Storage	Per GB-month

Reads and writes consume request units sized by the data involved and, for reads, the consistency level. Storage is billed per gigabyte-month. There are no nodes, clusters, or instance-hours; you pay for the requests and data, so an idle table costs only storage.

On-demand vs provisioned

On-demand mode charges per request and scales to zero, ideal for spiky, unpredictable, or new workloads. Provisioned mode reserves read and write capacity by the hour, cheaper per request for steady, predictable load, and auto-scaling adjusts it within bounds. The crossover is the same as DynamoDB on-demand versus provisioned: variable traffic favors on-demand, steady traffic favors provisioned.

Keyspaces vs self-managed Cassandra

Self-managed Cassandra costs instance-hours plus the substantial operational effort of running a distributed database. Keyspaces trades that for per-request billing and no operations. For teams without deep Cassandra expertise, or workloads that benefit from scaling to zero, Keyspaces often wins on total cost of ownership even where raw per-request pricing looks higher, because the operational cost of self-managed Cassandra is real and large.

Controlling Keyspaces cost

Choose the right capacity mode for your traffic, right-size provisioned capacity with auto-scaling, design efficient queries and data models to minimize request units, and manage storage growth. The levers are the same as any request-and-storage-billed database: fewer, more efficient operations and the correct capacity mode.

FAQ

How is Amazon Keyspaces priced?

By read and write request units (sized by the data involved and, for reads, consistency level) plus storage per GB-month, in either on-demand (per request, scales to zero) or provisioned (reserved capacity, cheaper for steady load) mode. There are no clusters or instance-hours.

On-demand or provisioned for Keyspaces?

On-demand for spiky, unpredictable, or new workloads, since it charges per request and scales to zero. Provisioned with auto-scaling for steady, predictable traffic, since reserving capacity is cheaper per request at consistent load. The crossover matches DynamoDB's on-demand versus provisioned decision.

Is Keyspaces cheaper than self-managed Cassandra?

Often, on total cost of ownership, because it removes the substantial operational effort of running a distributed Cassandra cluster. Even where per-request pricing looks higher than raw instance-hours, the eliminated operational cost, and scaling to zero, frequently make Keyspaces cheaper overall.

How do I reduce Keyspaces cost?

Choose the right capacity mode for your traffic, right-size provisioned capacity with auto-scaling, design efficient queries and data models to minimize request units consumed, and manage storage growth. Fewer, more efficient operations and the correct capacity mode are the main levers.

Does Keyspaces charge for idle tables?

Only storage. In on-demand mode there is no capacity charge, so an idle table costs just its per-GB-month storage. In provisioned mode you pay for reserved capacity whether used or not, so provisioned suits steady traffic where the reserved capacity is utilized.

Does C3X estimate Keyspaces cost?

C3X prices the Keyspaces resources in your Terraform, including provisioned capacity where set. Request volume and storage depend on usage, which you provide as assumptions, so on-demand cost and storage scale with your modeled traffic and data.

What to do next

Compare capacity modes before you deploy. C3X reads your Terraform and prices Keyspaces and the rest of your stack against a live catalog. Start with the quickstart.