Most engineers imagine failures as sudden events. A service crashes. A node goes down. An alert fires, and everyone jumps into action. In real high-availability Java systems, failures rarely behave that way. They almost always arrive quietly first.
Systems that have been running reliably for months or years begin to show small changes. Latency creeps up. Garbage collection pauses last a little longer. Thread pools spend more time near saturation. Nothing looks broken, and dashboards stay mostly green. Then one day, the system tips over, and the failure suddenly looks dramatic.