Conflict-free replicated datatypes (CRDTs)

are a family of data structures for sets, maps, ordered lists, counters, etc. that can be concurrently edited by multiple users, and which automatically resolve conflicts in sensible ways. Some CRDTs have been implemented in Riak 2.0

Mergeable Persisted Data Structures (MPDS)

track history explicitly, similarly to the Git version control system, and use a three-way merge function (whereas CRDTs use two-way merges).

Operational transformation (OT)

is the conflict resolution algorithm behind collaborative editing applications such as Etherpad and Google Docs. It was designed particularly for concurrent editing of an ordered list of items, such as the list of characters that constitute a text document.