Palo Alto Networks

Role: Software Engineer

College: Not Specified

Interview Date: Not Specified (blog post Aug 25, 2025)

Interview Type: Full-Time (through referral)

Result: Rejected

Difficulty: Hard

Rounds: 4 Rounds

Topics Asked: Online Coding, OOPS, Data Structures (Binary Tree, String manipulation, LRU Cache, Merge Overlapping Intervals), Networking (Sockets, Firewall concepts, App-ID, User-ID, NAT, SSL decryption, Multi-tenancy, Zone Protection Profiles), System Design, Behavioral

Experience:

This experience details a friend's interview process for a Software Engineer role at Palo Alto Networks, obtained through a referral. The process consisted of four distinct rounds.

Round 1 (Online Coding + OOPS + DS - 1 hr): A timed assessment with three questions:

• Write a function to remove nodes in a binary tree that have only one child. A follow-up asked, "why can't you just remove leaves also?"
• Anagram check or determine if a string can be rearranged into a palindrome.
• Implement a simple echo server using sockets in Python (a networking-style coding question).

Round 2 (Data Structures + Security Concepts - 1 hr): A video call that mixed Data Structures and Algorithms with firewall/security questions.

• Implement an LRU cache with TTL support.
• Merge overlapping intervals. A follow-up explored, "what if intervals are extremely large in count, how to optimize memory?"
• Explain App-ID versus policy-based filtering in a firewall.
• What is the use of User-ID in Palo Alto firewalls? The candidate initially stated it maps user to IP but realized they should have elaborated on policy enforcement per user or group instead of just IP address.

Round 3 (System Design + Network Concepts - 1.5 hr): This was considered the toughest round, a deep dive into design and security.

• Design a simple NAT service that translates private IPs to public.
• How to decrypt SSL traffic, scan it, and then re-encrypt before sending it to the destination.
• Explain multi-tenancy in firewall systems (VSYS vs Virtual Routers).
• Describe zone protection profiles and the types of attacks they defend against.

Round 4 (Behavioral + Tech Fit - 45 min):

• “Tell me about a production bug you fixed under pressure.”
• “Have you worked in a fast-moving environment with little documentation?”
• “Why Palo Alto Networks, and what excites you about network security?”

The candidate received a rejection due to sufficient coding skills, acceptable security concepts, but insufficient depth in system design and lack of detail in behavioral answers. The experience highlighted that Palo Alto interviews go beyond DSA, testing understanding of networks, security design, performance tradeoffs, and clear explanation of decisions.