The worst Kubernetes outage I keep seeing is not a node dying. It is a slow database, a liveness probe that talks to that database, and a cluster that then kills every pod that was still doing useful work.

Liveness does not mean “the app is healthy.” It means “this process is so stuck that Kubernetes should shoot it.” If you point that gun at a dependency, you will shoot the fleet.

In review I still see @Transactional used as a blessing: put it on a method, and the database will behave. It will not. Spring starts a transaction when a proxy intercepts an incoming call. If the call never hits the proxy, you have no transaction, no rollback, and a very confusing production bug.

What I believed → what I do now

I used to sprinkle @Transactional on every service method “to be safe.” I now put it on the one method that is the use-case boundary, I write a test that proves rollback, and I treat same-class private calls as a smell.