Interview experience for Round 1 (R1) – ServiceNow IC2 position

Position: Software Engineer (IC2)
Company: ServiceNow
Round: R1 – Technical Coding + Concepts
Background: I currently work as a Machine Learning Quality Engineer, prepping for a software engineer transition.

Round Format

• Live online technical round
• Topics: DSA, JavaScript, React, CS fundamentals
• Coding on a shared editor (JavaScript)

Questions & My Approach

1. Next Greater Element to the Right

• Question:
  Given an array, print for each element its next greater element to the right (or -1 if none exists).
  Example: [11, 13, 21, 3] → [13, 21, -1, -1]

• My Approach:

  • Explained both brute-force (O(n²)) and optimal stack (O(n)) solutions.
  • Implemented the monotonic stack solution in JavaScript—clean, commented, CP-style.
  • Discussed edge cases like decreasing sequences and duplicates.
  • Provided reasoning and time/space complexity.

2. First Missing Positive Integer

• Question:
  Given an unsorted array, find the smallest missing positive integer starting from 1, in O(n) time and O(1) space.
  Example: [2, 3, -7, 6, 8, 1, -10, 15] → 4

• My Approach:

  • Described classic O(n) in-place hashing (index marking) approach.
  • Walked through a dry run, showed how negatives and out-of-bounds numbers are handled.
  • Wrote JS function signatures and code.
  • Highlighted edge cases (no 1 present, fully continuous arrays, all negatives).
  • Explained why this approach meets O(n)/O(1) requirements.

3. JavaScript & React Concepts

• Promises:

  • Explained promise states (pending/fulfilled/rejected), usage, chaining, and async/await.

• Callbacks:

  • Discussed as arguments for async ops, in React (event handlers, child-to-parent comm), and array methods.

• useEffect & useMemo:

  • Gave clear definitions, syntax, use cases, and sample code.
  • Explained when and why to use each for performance and side effects.

4. JS Fundamentals

• call, apply, bind:

  • Compared usage, argument passing, and context binding.

• Private Variables/Closures:

  • Demonstrated classic closure and ES6+ class fields.

• IIFE:

  • Explained syntax, use cases for local scope/data privacy.

• Hoisting:

  • Clarified what’s hoisted, difference between var/let/const, TDZ.

• Synchronous vs. Asynchronous:

  • Explained default JS sync nature, async via event loop/callbacks/promises.

5. Closure Coding Challenge

• Task:
  Implement a closure-based counter so each call returns the next increment.

• Solution:

  • Wrote a factory function returning an inner function that remembers a private counter.

How I Approached the Round

• Explained my thinking before coding, highlighted time/space tradeoffs.
• Used CP-style variable names and code structure.
• Gave edge cases, reasoning, and small dry runs for clarity.
• Related answers back to real ServiceNow product scenarios (edge-case bugs, async APIs, UI interactions).

Overall Impression

• Questions were practical, relevant, and tested core understanding.
• Clear communication and explaining the "why" as well as the "how" was appreciated.
• Prepping with LeetCode, React core, and real-world debugging scenarios helped a lot.

Advice:
If you’re prepping for ServiceNow IC2 or similar roles, focus on:

• Mastering DSA patterns (esp. stacks, hash maps, in-place tricks)
• Explaining JS/React fundamentals in detail
• Practicing clear, concise code and justifying your choices

Note: R2 -> Link