Module vector_hybrid 

Hybrid vector backend: hot HNSW cache + cold DiskANN store.

Implements the “map of maps” pattern: HNSW holds the frequently-accessed vectors for fast lookup, while DiskANN holds the full corpus. Vectors are promoted from cold to hot based on access frequency, and evicted from the hot tier using LRU when it reaches capacity.

Hardening features (Cognitum Seed WS1)

Epoch, tombstone, and capacity operations are delegated to the cold (authoritative) tier. The hot tier mirrors soft-deletes to keep search results consistent.

Compiled only when the ecc feature is enabled.

Structs

HybridBackend

Hybrid vector backend combining HNSW (hot) + DiskANN (cold).

HybridConfig

Hybrid backend configuration.

Enums

EvictionPolicy

Eviction policy for the hot tier.