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Interview questions from top companies, mapped to the exact round they show up in. Prep for what you will actually face.

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Online AssessmentDSA / CodingMachine CodingLow-Level Design

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The Loop aggregates publicly shared interview experiences and curated commonly-asked questions, each labeled with its source. Not affiliated with any company listed.

CC BY-NC 4.0 · © 2026

← Mastercard

Mid Backend at Mastercard

BackendMidOffer◆ Commonly asked· 2025

A mid backend loop. Fast-paced; expect follow-ups that push on depth.

The loop · 5 rounds

01

Round 01 · 3 questions

DSA / Coding

Data structures & algorithms on a whiteboard or shared editor.

  • Diameter of a binary tree.
    MidEasy◆ Commonly asked
    #tree#dfs
    PracticeLeetCode↗GeeksforGeeks↗
  • Meeting rooms II — minimum rooms required.
    MidMedium◆ Commonly asked
    #heap#intervals
    PracticeLeetCode↗GeeksforGeeks↗
  • Best time to buy and sell stock.
    MidEasy◆ Commonly asked
    #array#greedy
    PracticeLeetCode↗GeeksforGeeks↗
02

Round 02 · 2 questions

Machine Coding

Build a working component or service under time pressure.

  • Build an in-memory pub/sub with topic subscriptions.
    MidMedium◆ Commonly asked
    #pub-sub
    PracticeGeeksforGeeks↗Search↗
  • Implement a token-bucket rate limiter as a service.
    MidMedium◆ Commonly asked
    #rate-limit
    PracticeGeeksforGeeks↗Search↗
03

Round 03 · 1 question

Low-Level Design

Object-oriented / low-level design of a focused module.

  • Design an elevator control system.
    MidMedium◆ Commonly asked
    #oop#state-machine
    PracticeGeeksforGeeks↗Search↗
04

Round 04 · 3 questions

Tech Deep-Dive

Deep questions on your core stack and fundamentals.

  • Caching strategies: cache-aside, write-through, TTLs.
    MidMedium◆ Commonly asked
    #cache
    PracticeGeeksforGeeks↗Search↗
  • How do you retry without amplifying load?
    MidHard◆ Commonly asked
    #reliability
    PracticeGeeksforGeeks↗Search↗
  • Explain connection pooling and why it matters.
    MidMedium◆ Commonly asked
    #databases
    PracticeGeeksforGeeks↗Search↗
05

Round 05 · 2 questions

Behavioral / HR

Values, collaboration, and past-experience (STAR) questions.

  • Describe mentoring or unblocking another engineer.
    Mid◆ Commonly asked
    #mentorship#star
  • When did you change your mind after seeing new evidence?
    Mid◆ Commonly asked
    #judgment#star

Practice each round across every company

  • DSA / Coding
  • Machine Coding
  • Low-Level Design
  • Tech Deep-Dive
  • Behavioral / HR

◆ This experience is composed from commonly reported questions for this role and level. Real, individually-shared interviews will be layered in over time.