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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

← Reddit

Mid Backend at Reddit

BackendMidOutcome unknown◆ Commonly asked· 2023

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.

  • Diameter of a binary tree.
    MidEasy◆ Commonly asked
    #tree#dfs
    PracticeLeetCode↗GeeksforGeeks↗
  • Subsets.
    MidMedium◆ Commonly asked
    #backtracking
    PracticeLeetCode↗GeeksforGeeks↗
  • Sliding window maximum.
    MidHard◆ Commonly asked
    #deque#sliding-window
    PracticeLeetCode↗GeeksforGeeks↗
02

Round 02 · 2 questions

Machine Coding

Build a working component or service under time pressure.

  • Build an in-memory rate limiter as a middleware.
    MidMedium◆ Commonly asked
    #rate-limit#middleware
    PracticeGeeksforGeeks↗Search↗
  • Build a CSV importer that streams and validates rows.
    MidMedium◆ Commonly asked
    #streaming#validation
    PracticeGeeksforGeeks↗Search↗
03

Round 03 · 1 question

Low-Level Design

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

  • Design classes for a parking lot.
    MidMedium◆ Commonly asked
    #oop#design-patterns
    PracticeGeeksforGeeks↗Search↗
04

Round 04 · 3 questions

Tech Deep-Dive

Deep questions on your core stack and fundamentals.

  • Compare rate-limiting algorithms and their trade-offs.
    MidMedium◆ Commonly asked
    #rate-limit
    PracticeGeeksforGeeks↗Search↗
  • How do you retry without amplifying load?
    MidHard◆ Commonly asked
    #reliability
    PracticeGeeksforGeeks↗Search↗
  • Explain leader election and consensus (Raft) at a high level.
    MidHard◆ Commonly asked
    #distributed#consensus
    PracticeGeeksforGeeks↗Search↗
05

Round 05 · 2 questions

Behavioral / HR

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

  • Tell me about the hardest bug you have debugged.
    Mid◆ Commonly asked
    #debugging#star
  • Tell me about a project you are most proud of.
    Mid◆ Commonly asked
    #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.