Zscaler interview process (2026)

Round-by-round breakdown of the Zscaler software engineering interview across 4 levels and 19 rounds: interview mode, sample questions, and worked solutions.

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Software Engineer Intern (Dev C/C++) — campus

Difficulty: Medium · Timeline: ~2-4 weeks (drive) · Recommended prep: 4-6 weeks

  1. Round 0: Online Assessment (coding)

    Assessment · ~2 hours · difficulty 3/5 · elimination round

    Mode of interview: Online assessment

    Sample question: Maximum XOR of a pair - Given an array of non-negative integers, return the maximum value of a[i] XOR a[j] over all pairs. Aim for better than O(n^2) (bit-prefix or trie approach).

  2. Round 1: Technical interview 1 - DSA + OS/networking basics

    Onsite · ~45 min · difficulty 3/5

    Mode of interview: Onsite or virtual onsite interview

    Sample question: Search a 2D Matrix II - Given an m x n matrix where each row is sorted left to right and each column is sorted top to bottom, determine whether a target value exists in the matrix in O(m+n).

  3. Round 2: Technical interview 2 - C/C++ and pointers

    Onsite · ~45 min · difficulty 3/5

    Mode of interview: Onsite or virtual onsite interview

    Sample question: IP string to 32-bit integer - Given an IPv4 address as a string (e.g. "17.172.224.47"), validate it and convert it into its 32-bit unsigned integer representation without using library conversion helpers.

  4. Round 3: Managerial + HR round

    Behavioral · ~45 min · difficulty 1/5

    Mode of interview: Live behavioral interview

Associate Software Engineer (new grad) — India

Difficulty: Medium · Timeline: ~2-4 weeks · Recommended prep: 6-8 weeks · Cooldown: ~6 months

  1. Round 0: Online Assessment (HackerRank)

    Assessment · ~130 min · difficulty 3/5 · elimination round

    Mode of interview: Online assessment · HackerRank

    Sample question: Design a Min Stack - Implement a stack supporting push, pop, top and getMin, each in O(1) time. Process a sequence of operations and print the result of every top and getMin call.

  2. Round 1: Technical round 1 - CS fundamentals

    Onsite · ~30-45 min · difficulty 3/5

    Mode of interview: Onsite or virtual onsite interview

    Sample question: You type a URL into a browser on a corporate laptop - walk through everything that happens: DNS resolution, TCP handshake, TLS negotiation, HTTP request, and which OSI/TCP-IP layer each step belongs to.

  3. Round 2: Technical round 2 - deep C++ and systems

    Onsite · ~90-120 min · difficulty 4/5

    Mode of interview: Live interview · HackerRank CodePair

    Sample question: Endianness check and byte swap - Write a program that detects whether the host machine is little- or big-endian, then converts a given 32-bit unsigned integer between network byte order and host order without using htonl/ntohl.

  4. Round 3: Technical round 3 - mixed panel

    Onsite · ~45-60 min · difficulty 3/5

    Mode of interview: Onsite or virtual onsite interview

    Sample question: In-place run-length encoding - Given a character array like [a,a,b,b,b,c], compress it in place to [a,2,b,3,c] and return the new length, using O(1) extra space.

  5. Round 4: HR / fit round

    Behavioral · ~20-30 min

    Mode of interview: Live behavioral interview

Software Engineer (2-5 yrs) — India

Difficulty: Medium · Timeline: ~3-5 weeks · Recommended prep: 6-8 weeks · Cooldown: ~6 months

  1. Round 0: Recruiter screen

    Phone · ~30 min

    Mode of interview: Remote phone or video interview

  2. Round 1: Online assessment / coding screen

    Assessment · ~60-120 min · difficulty 3/5 · elimination round

    Mode of interview: Online assessment · HackerRank

    Sample question: Merge Intervals - Given a list of intervals, merge all overlapping intervals and print the resulting disjoint intervals in sorted order.

  3. Round 2: DSA + core CS round

    Onsite · ~60 min · difficulty 3/5

    Mode of interview: Onsite or virtual onsite interview

    Sample question: Search in Rotated Sorted Array - Given a sorted array rotated at an unknown pivot and a target value, return the index of the target in O(log n), or -1 if absent.

  4. Round 3: Networking / systems deep-dive

    Onsite · ~60 min · difficulty 4/5

    Mode of interview: Onsite or virtual onsite interview

    Sample question: Trace a packet through a cloud secure-web-gateway: a user in a Mohali office opens https://example.com through a forward proxy that does TLS inspection. Describe each hop and transformation - DNS, tunnel to the nearest PoP, TLS interception with a re-signed certificate, policy evaluation, and the return path. Where would you look first if users report intermittent slowness?

  5. Round 4: Hiring manager + behavioral

    Behavioral · ~45-60 min · difficulty 2/5

    Mode of interview: Live behavioral interview

Senior Software Engineer — India

Difficulty: Hard · Timeline: ~3-5 weeks · Recommended prep: 8-10 weeks · Cooldown: ~6-12 months

  1. Round 0: Recruiter screen

    Phone · ~15-30 min

    Mode of interview: Remote phone or video interview

  2. Round 1: Technical phone screen (coding)

    Phone · ~60 min · difficulty 3/5 · elimination round

    Mode of interview: Remote phone or video interview

    Sample question: Top-K frequent destinations - Given a stream of proxy log lines (client_ip, destination_domain), return the K most-frequented destination domains. Discuss the heap vs bucket approaches and how you would shard this if the log volume were billions of lines per day.

  3. Round 2: Coding + concurrency with Principal Engineers

    Onsite · ~60 min · difficulty 4/5

    Mode of interview: Onsite or virtual onsite interview

    Sample question: Thread-safe LRU cache - Implement an LRU cache with get/put in O(1) that is safe under concurrent access. Explain your locking strategy (single mutex vs sharded locks), what changes for a read-heavy workload, and how you would add TTL-based eviction.

  4. Round 3: System design (cloud-scale)

    System_design · ~60 min · difficulty 4/5

    Mode of interview: Live system design interview

    Sample question: Design the logging and analytics pipeline for a global cloud proxy: every PoP emits per-transaction logs (hundreds of billions/day). Design ingestion, transport, hot/cold storage, and a near-real-time dashboard where a tenant admin can query their own traffic within seconds. Cover partitioning by tenant, backpressure, PoP-level failures and cost controls.

  5. Round 4: Hiring manager round

    Behavioral · ~45-60 min · difficulty 2/5

    Mode of interview: Live behavioral interview

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Worked sample solutions (code, design diagrams, and STAR answers) for every round are available in the FAANGPlus app: open interview processes.