I had a similar task to
"Set up a web service, load balancer and infrastructure to scale it to handle a large amount of requests. Harden the security of it to the best of your ability. Document how it works, how to scale it, why you built it the way you did, what measures you took to harden it and why, and any future improvements you would suggest. All code and documentation should be production quality. This should take about four hours."
Maybe you can write this code in four hours, but all this documentation and motivation as well? Fuck off.
They also asked for a made up report from a security audit (this was for a security engineer position) containing a dozen realistic vulnerabilities with descriptions, impact assessments, and remediation suggestions. Once again of production quality. This is at least six pages of highly technical, well researched, and carefully worded text. Four hours is tight for this task alone.
You can run systemd (or cron) inside a pod for scheduling and call the kubernetes API from there to run jobs and stuff. Not sure if this helps you, but it can be easy to overlook.