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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

← Retool

Mid Backend at Retool

BackendMidNo offer◆ Commonly asked· 2023

A mid backend loop. Coding-heavy early, design and behavioral later.

The loop · 5 rounds

01

Round 01 · 3 questions

DSA / Coding

Data structures & algorithms on a whiteboard or shared editor.

  • Invert a binary tree.
    MidEasy◆ Commonly asked
    #tree
    PracticeLeetCode↗GeeksforGeeks↗
  • Longest substring without repeating characters.
    MidMedium◆ Commonly asked
    #sliding-window#string
    PracticeLeetCode↗GeeksforGeeks↗
  • Coin change — fewest coins to make an amount.
    MidMedium◆ Commonly asked
    #dp
    PracticeLeetCode↗GeeksforGeeks↗
02

Round 02 · 2 questions

Machine Coding

Build a working component or service under time pressure.

  • Build a webhook receiver with signature verification.
    MidMedium◆ Commonly asked
    #security#api
    PracticeGeeksforGeeks↗Search↗
  • Build a key-value store with TTL expiry.
    MidMedium◆ Commonly asked
    #cache#ttl
    PracticeGeeksforGeeks↗Search↗
03

Round 03 · 1 question

Low-Level Design

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

  • Design a hotel-reservation system core.
    MidMedium◆ Commonly asked
    #oop#concurrency
    PracticeGeeksforGeeks↗Search↗
04

Round 04 · 3 questions

Tech Deep-Dive

Deep questions on your core stack and fundamentals.

  • Explain eventual consistency with a real example.
    MidHard◆ Commonly asked
    #distributed
    PracticeGeeksforGeeks↗Search↗
  • How does a load balancer choose a backend?
    MidMedium◆ Commonly asked
    #networking
    PracticeGeeksforGeeks↗Search↗
  • How do you design an idempotency-key system for payments?
    MidHard◆ Commonly asked
    #idempotency#payments
    PracticeGeeksforGeeks↗Search↗
05

Round 05 · 2 questions

Behavioral / HR

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

  • Tell me about a time you had to learn something quickly.
    Mid◆ Commonly asked
    #learning#star
  • Why this company, and why this role?
    Mid◆ Commonly asked
    #motivation

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.