Labs and other environments where I turn what I do at work into code.
A Proxmox hypervisor administered entirely with Ansible. I set up the services, back them up and then cause a disaster on purpose to prove the restore actually works.
Six VLANs behind an OPNsense where the allowed flows are declared in one file. I don't write the deny rules, the code computes them by subtracting what's allowed from every possible combination, and a suite tests, one by one, the 266 that must fail.
Monitoring as code. I bring up a complete Zabbix with one command, and hosts and alerts are defined through the API instead of by clicking around.
A complete Windows domain brought up and administered from PowerShell instead of the GUI. Repeatable, auditable and hardened in line with the CIS Benchmark.
A three-node Kubernetes cluster I bring up from code, govern from Git and break on purpose with four timed drills. The last one destroys all three nodes, and everything comes back, data included, in under ten minutes.
The site you're looking at runs on an Azure VM that I built and administer myself. AlmaLinux, Nginx, HTTPS with Let's Encrypt and Cloudflare in front, all configured by hand. If it goes down at 3 a.m., the one who SSHes in is me.