Causal consistency.
also: causally consistentOperations that are causally related (a reply after the post it answers) are seen in that order by everyone; concurrent ones may differ.
the two-minute refresher
- A happens before B if same process A first, if B reads A's write, or transitively.
- Nobody sees a reply before the message it replies to.
- Concurrent, unrelated operations may appear in different orders on different nodes.
- Tracked with dependency metadata such as vector clocks.