Last Write Wins (LWW)
Summary: A simple conflict resolution strategy where the most recent write (based on a timestamp) is kept, and older writes are discarded.
Sources: chapter5, chapter8
Last updated: 2026-04-17
Last Write Wins (LWW) is a strategy for achieving eventual convergence by declaring that only the “most recent” value will be kept, and all other concurrent writes will be discarded (source: chapter5, p. 186).
Risks and Limitations
While LWW is simple to implement, it has significant drawbacks:
- Data loss: If two writes happen very close together, the one with the smaller timestamp is discarded, even if it might have contained important information (source: chapter5, p. 186).
- Durability issues: If several writes are reported as successful to the client, but only one is eventually kept, the other writes are effectively lost (source: chapter5, p. 186).
- Clock skew: LWW relies on the accuracy of timestamps. If clocks on different nodes are not perfectly synchronized, a write that happened later (causally) might be assigned an earlier timestamp and be silently discarded. This can cause data to “mysteriously disappear” when a node with a lagging clock is unable to overwrite values written by a node with a fast clock (source: chapter8, p. 292).
- Sequential writes: LWW cannot distinguish between writes that occurred sequentially in quick succession and writes that were truly concurrent (source: chapter8, p. 292).