Couchbase

Couchbase is a JSON document database offered as Capella database-as-a-service or as self-managed Couchbase Server, with an in-memory architecture and a query language, SQL plus plus, that gives SQL syntax over document data.

SQL plus plus is a more significant choice than it sounds. The main practical objection to document databases has always been that an organisation's analysts, reporting tools and existing code all speak SQL, and adopting a new query language means retraining people and rewriting integrations. Providing SQL syntax over JSON removes most of that cost while keeping the flexible schema, which is why this design keeps reappearing across the category.

Reaching the edge is the other distinguishing capability. Couchbase Mobile is an embedded NoSQL database with cloud-to-edge synchronisation and offline-first behaviour, and Couchbase Edge Server targets resource-constrained environments. An application that must keep working on a device with no connectivity, then reconcile when the network returns, is otherwise a hand-built synchronisation project, and those are notoriously difficult to get right.

The AI Data Plane is the newest addition, providing agent memory, governed tool access and Model Context Protocol support on the same platform, which places the data controls where an agent actually reaches for data. Search covers full-text, hybrid, geospatial and vector queries, and Analytics handles real-time multisource work. A Kubernetes Operator, SDKs and the Capella iQ assistant support development. Capella Basic starts at 0.15 dollars an hour per node, Developer Pro at 0.35 dollars and Enterprise at 0.49 dollars, with higher rates on other service tiers.