The Data Service provides access to data. It supports the storing, setting, and retrieving of data-items, specified by key.
The Data Service is the most fundamental of all Couchbase services, providing read/write access to data in memory and on disk. The Data Service stores data items in Buckets. Before an item can be saved, a bucket must exist for it. Buckets only exist on nodes that run the Data Service.
The Data Service must run on at least one node of every cluster. However, at least three nodes are required for production environments. (Clusters with less than three Data nodes have several limitations.)
The Data Service provides a fully integrated in-memory caching layer, which provides high-speed data access. Couchbase Cloud supports the Couchbase bucket type, which means that all data items are written to memory and persisted to disk. The Data Service manages memory to ensure high performance and scalability: memory quotas are established, and data not recently used can be ejected, to make room for data more frequently requested. You can configure a memory quota that provides caching for all or a portion of stored data items.
Read more about Memory and Storage.
Couchbase Server uses buckets to group collections of keys and values logically. Buckets must be created before you can store any data. A maximum of 10 buckets can be created per cluster.