# Keyspaces (Apache Cassandra)

- **Docs**: https://docs.aws.amazon.com/keyspaces/
- **Docs (llms.txt)**: https://docs.aws.amazon.com/keyspaces/latest/devguide/llms.txt
- **Data model**: Wide-column (partition key + clustering columns)
- **Query language**: CQL (Cassandra Query Language)
- **Compatibility**: Apache Cassandra compatible (CQL, open-source Cassandra drivers)
- **Serverless**: Yes (on-demand and provisioned capacity)
- **Serverless type**: Operations — no cluster to manage, create a keyspace and start writing; capacity scales automatically
- **Scale to zero**: Yes (on-demand: throughput scales to zero; storage still billed)
- **VPC required**: No (VPC endpoints supported)
- **Multi-region**: Multi-Region replication (add/remove Regions on a live keyspace)
- **Consistency**: Tunable reads (ONE, LOCAL_QUORUM); lightweight transactions (LWT) for conditional writes
- **Free Tier**: First three months (30M write request units, 30M read request units, 1 GB storage per month).
- **Min cost**: $0 (free tier)
- **Pricing**: On-demand and provisioned; AWS Database Savings Plans supported
- **Time to first query**: Seconds (create table, start writing)
- **Key features**: CQL compatibility, serverless, replication across 3 AZs, multi-Region replication, TTL, point-in-time recovery, CDC Streams (pull API), client-side timestamps, logged batches, User Defined Types (UDTs) including nested UDTs, frozen collections, pre-warming, IPv6, customer-managed KMS keys
- **Limitations**: No JOINs, no secondary indexes, no full-text search, no complex analytical queries, per-row 1 MB size, some CQL features unsupported
- **Best for**: Cassandra migrations, CQL/Cassandra-driver applications, high-throughput write-heavy workloads, event-driven pipelines via CDC Streams, IoT device registries, fleet and time-series-style data already modeled in CQL
- **Not for**: Relational/transactional joins, full-text search, analytics, teams without a CQL/Cassandra requirement (DynamoDB is the default key-value choice)