Deltafed

Deltafed is an open-standard and set of reference implementations for delta-based federation of distributed data stores and services. It is designed to enable autonomous servers to exchange only the changes (deltas) that occur since the last synchronization, rather than full data transfers. The approach reduces bandwidth usage and storage growth in federated networks where many nodes maintain similar datasets, such as federated social networks, collaborative editing platforms, or distributed catalogs.

Deltafed defines a common data model and a delta encoding format for representing insertions, deletions, and updates. The federation protocol specifies message types for publishing deltas, requesting missing changes, and acknowledging delivery. A reconciliation layer handles out-of-order deliveries and conflict resolution through last-writer-wins, vector clocks, or application-specific strategies.

Security and privacy considerations include mutual authentication between nodes, transport encryption, and access controls for published deltas. The system supports provenance and auditable histories through signed deltas and immutable logs.

Architecture typically includes node roles such as publishers (originating data changes), subscribers (receiving updates), and federation relays or brokers that help route delta streams. References implementations are available in multiple languages and may be embedded in larger federated ecosystems or used as a standalone synchronization layer.

Deltafed is experimental in many communities, with ongoing work focused on interoperability between implementations and performance tuning. See also delta encoding, federation, Fediverse, distributed systems.