Expand description
Hybrid Logical Clock.
Canonical timestamp for replicated metadata entries, descriptor
modification times, and descriptor lease expiry. Monotonic across
wall-clock skew: update folds a remote HLC into the local clock so
causally later events always receive a strictly greater timestamp.
Metadata DDL is not a hot path (hundreds per second at most), so the clock is backed by a short-lived mutex rather than atomics.