Vector clock
Per-node logical counter; comparing two clocks tells you happens-before vs concurrent.
Origin
Colin Fidge and Friedemann Mattern independently introduced vector clocks in 1988. Generalises Lamport timestamps to detect concurrent (vs causally-ordered) events.
Where it shows up in production
- Amazon Dynamo Used vector clocks for conflict detection on writes. Successors often switched to dotted version vectors.
- Riak Vector clocks track sibling versions during conflicts.
- Hybrid Logical Clocks CockroachDB / YugabyteDB combine wall clock + vector-clock-like counters.
Sources & further reading
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