Neo4j.ClientError.TransientError.TransactionDeadlockDetected during rolling upgrade of causal cluster
Goal: achieve a seamless version upgrade of a three‑node Neo4j causal cluster without noticeable downtime for a small write‑heavy application. Constraint: during a rolling upgrade old and new nodes run different protocol versions, which can increase lock‑contention and trigger the transient TransactionDeadlockDetected error; the application must distinguish