17 years ago I built a system to automatically consolidate and pre-processed data from various sources. It saved 20 man-hours a day of effort and downtime. Put in 12 hours of support over the 2 years it stayed under my management, while I took many hits about how "badly" it was designed and how other teams could improve it. Moved on from that role.

6 years after left the role, I got a call from a sysadmin. He told me the machine that hosted the system went down but they managed to recover the HDD and restore it into a VM. I was surprised because I thought they had decommissioned it long ago, when the vultures who wanted to pad their KPIs tried to write a better version. He said multiple efforts all failed and no one was able to replicate what that system does. The reason he gave me a call is because after they loaded the HDD into a VM and turned everything back on, the system came back online and was working perfectly without any effort on his part. He was astounded and just wanted to talk to the person who was able to build a system that literally wouldn't die.

It wasn't the most elegant or best designed system, but I designed it not to die and that's exactly what I got!