Two services start the same batch job at the same time. Both read the same data, both process it, both write conflicting results. Your database row lock didn’t help because the services are on different JVMs. This is the distributed lock problem. Why Database Locks Don’t Work Here A SELECT FOR UPDATE on a MySQL row holds a lock only for the lifetime of that connection. Cross-service, that’s useless. You’d need a shared coordination point, something every instance can talk to.