Security
Kernel and driver security software, then my own systems
At Mutiny Digital Group I spent three and a half years as a senior software engineer on Windows kernel-mode and driver security software, along with the reverse engineering that work depends on. It shipped to more than 1,000 users.
I bring the same habits to everything I run now. I harden my own servers and keep deploys staged, dev first and then production. For my own data I built a tamper-evident integrity system: hash chains keyed with a secret, checked against a witness server on a separate machine, so tampering is detected and repaired on its own.