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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.

MIT · © 2026

← MongoDB

Mid Backend at MongoDB

BackendMidNo offer◆ Commonly asked· 2024

A mid backend loop. Fundamentals mattered as much as getting to an answer.

The loop · 5 rounds

01

Round 01 · 3 questions

DSA / Coding

Data structures & algorithms on a whiteboard or shared editor.

  • Validate a binary search tree.
    MidMedium◆ Commonly asked
    #tree#dfs
    PracticeLeetCode↗GeeksforGeeks↗
  • Course Schedule — detect a cycle / topological sort.
    MidMedium◆ Commonly asked
    #graph#topo-sort
    PracticeLeetCode↗GeeksforGeeks↗
  • Word break.
    MidMedium◆ Commonly asked
    #dp#string
    PracticeLeetCode↗GeeksforGeeks↗
02

Round 02 · 2 questions

Machine Coding

Build a working component or service under time pressure.

  • Implement a token-bucket rate limiter as a service.
    MidMedium◆ Commonly asked
    #rate-limit
    PracticeGeeksforGeeks↗Search↗
  • Implement an exponential-backoff HTTP client.
    MidMedium◆ Commonly asked
    #reliability
    PracticeGeeksforGeeks↗Search↗
03

Round 03 · 1 question

Low-Level Design

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

  • Design a rate limiter (classes + interfaces).
    MidMedium◆ Commonly asked
    #oop#rate-limit
    PracticeGeeksforGeeks↗Search↗
04

Round 04 · 3 questions

Tech Deep-Dive

Deep questions on your core stack and fundamentals.

  • Explain the CAP theorem with a practical example.
    MidHard◆ Commonly asked
    #distributed
    PracticeGeeksforGeeks↗Search↗
  • How does a bloom filter work and when would you use one?
    MidMedium◆ Commonly asked
    #data-structures#probabilistic
    PracticeGeeksforGeeks↗Search↗
  • How do you design a public API for backward compatibility?
    MidMedium◆ Commonly asked
    #api-design
    PracticeGeeksforGeeks↗Search↗
05

Round 05 · 2 questions

Behavioral / HR

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

  • Describe a goal you set and how you achieved it.
    Mid◆ Commonly asked
    #ownership#star
  • Why this company, and why this role?
    Mid◆ Commonly asked
    #motivation

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