Odcisn

Odcisn is a theoretical construct in distributed computing used to describe a protocol for synchronizing cached state across replicated systems. It denotes an approach called Ordered Deterministic Cache Synchronization Node, a protocol layer that aims to ensure updates propagate to all replicas in a single, deterministic order. This ordering is intended to make the outcome of concurrent updates easier to reason about and to reduce the likelihood of divergent states.

The term odcisn appears to be an acronym coined for this concept, with the root word odcisk meaning imprint in several Slavic languages. The name was chosen to evoke the idea of a consistent “imprint” of state that reappears across nodes when updates are applied.

The concept emerged in theoretical discussions and related experimental papers published around 2019–2020, as researchers explored alternatives to traditional consensus-based cache invalidation. While not yet standardized, odcisn has been described as complementary to existing models such as CRDTs (conflict-free replicated data types) and vector clocks, offering a deterministic ordering mechanism rather than reliance on eventual convergence alone.

Key features attributed to odcisn include a global sequence space for operations, a lightweight dissemination protocol (often gossip-based) to share sequence information, and a deterministic total order in which updates are applied. It is designed to integrate with existing storage engines and caches while providing clearer guarantees about state convergence.

Adoption remains limited to experimental settings and prototype deployments. Criticisms focus on added latency, implementation complexity, and the challenge of scaling the global order in large, geo-distributed systems.

See also: CRDT, vector clock, Lamport clock, cache invalidation, distributed database.