Glossary
Event Ordering Guarantee
An event ordering guarantee states whether a system promises to process events in the order they actually happened, or makes no such promise and allows events to arrive and be processed out of sequence. Many distributed and event-driven systems deliberately don't guarantee strict ordering, because guaranteeing it is expensive and unnecessary for most of what the events are used for.
This becomes an authorization problem specifically when a decision depends on sequence: a permission-revoked event that arrives and gets processed after a later action-attempted event it should have preceded can leave that later action authorized under a permission that, in the actual timeline of what happened, no longer existed by the time the action occurred. A system making sequence-dependent authorization decisions needs to know explicitly whether its event pipeline actually guarantees ordering, rather than assuming events simply arrive in the order they happened.