Unfortunately, it was a waste of time.

They only give 72 hours to complete a challenge. How is this possible while working for another company?

After the challenge, you plan the tech interview. After a couple of days, they cancel it because "they found someone new."

What is the sense of this process?

It's not planned to be equitable; it favors the unemployed or people with poor work-life balance, which, I believe, is the situation in the company.

Secure Docker & K8s manifests. Give architecture blueprint. Write documentation.