When integrating JWT auth, JPA persistence, Redis caching, and Kafka events into one production service, what's the most common integration bug?

Ordering and transactionality: publishing a Kafka event before the database transaction that created the underlying row has actually committed means a consumer can react to an event for data that doesn't exist yet if it reads too fast. The safe pattern is publishing the event only after the transaction commits (e.g. via a transactional outbox or `@TransactionalEventListener(phase = AFTER_COMMIT)`).