{"id":"event-store-single-writer-assumption","text":"The event store's `expected_version` check-then-act pattern in `append` and `append_batch` has no locking, making the optimistic concurrency guard safe only under a single-writer concurrency model — concurrent writers create a TOCTOU race","truth_value":"IN","source":"entries/2026/05/29/topic-event-sourcing-concurrency-model.md","source_url":"","source_hash":"","justifications":[],"dependents":[],"metadata":{},"explanation":{"steps":[{"node":"event-store-single-writer-assumption","truth_value":"IN","reason":"premise"}]}}