Palo Alto Networks Mid-level Engineer: algorithm screen, OS and networking questions, API Rate Limiter LLD and URL shortener HLD

The first round was a class algorithm challenge. I was asked two questions. The first was to invert a binary tree and the second was to sort an array. It was pretty straightforward if you have grinded DSA for a bit. If you haven't done that it could be hard to complete it on time.

I got an email saying I passed and that I had to schedule a recruiter call which was pretty short, like 20 minutes, where they asked the standard behavioral questions covered here. One recommendation is to make sure you prepare why cyber security is important because they definitely asked about that.

The next round was a technical interview where I discussed recent projects I had worked on in my old company as well as technical questions around operating systems and networking so definitely prepare those if you haven't already.

The last technical round was a virtual onsite where I was asked a LLD and HLD question. The LLD was to design an API Rate Limiter which was pretty standard and nothing too hard and there wasn't much time pressure here. The HLD was also pretty basic, just a URL shortener, so if you've done some prep you'll be fine.

There was a final behavioral call a few days later where they went through motivations and working style. They were very quick getting back and I got an offer a few days later.