3 Spring annotations I can never forget, because they broke in prod.
1. @Transactional
I called it from another method in the same class.
Spring wraps the bean in a proxy, like a gate outside it. this.method() walks around the gate.
No transaction, no rollback. The order failed, but the other two tables stayed updated.
Fix: Move the method to another bean or service, so the call goes through the proxy.
2. @Scheduled
Fine on one pod.
On 4 pods, the same cron ran on all of them. Duplicate notifications 💀
Fix: Redis lock + idempotency check. The lock decides who starts, and all the others are blocked.
3. @Lazy
It killed the circular dependency error in 2 minutes.
The same pattern showed up again a week later. It hid the problem instead of fixing it.
Fix: Break the loop with events. ✅
Using an annotation is easy. Understanding how it works is equally important.