Locally
You can replicate local databases on-device — see: Intra-device Data Sync
Centrally
You can sync with a centralized Couchbase Server database using Sync Gateway — see: Remote Sync using Sync Gateway
At the edge
You can sync directly with other edge devices, peer-to-peer, using a listener to interact with the Couchbase Lite replicator — see: Landing P2Psync