- Apache CouchDB is a scalable key-value store that uses peer-based replication for data synchronization. It uses an append-only file structure and is designed to be crash resilient. - CouchDB stores data as JSON documents and uses JavaScript based map-reduce functions to index and query the documents. The API is RESTful and uses HTTP. - CouchDB is optimized for web applications by allowing data access with low latency and enabling fully replicated applications that can scale from a single machine to a cluster of servers.