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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

← Slack

Senior Backend at Slack

BackendSeniorRejected◆ Commonly asked· 2024

A senior backend loop. Balanced across coding, design, and collaboration.

The loop · 6 rounds

01

Round 01 · 3 questions

DSA / Coding

Data structures & algorithms on a whiteboard or shared editor.

  • Same tree.
    SeniorEasy◆ Commonly asked
    #tree
    PracticeLeetCode↗GeeksforGeeks↗
  • Find median from data stream.
    SeniorHard◆ Commonly asked
    #heap#design
    PracticeLeetCode↗GeeksforGeeks↗
  • Reverse a linked list.
    SeniorEasy◆ Commonly asked
    #linked-list
    PracticeLeetCode↗GeeksforGeeks↗
02

Round 02 · 2 questions

Machine Coding

Build a working component or service under time pressure.

  • Build a REST endpoint with pagination, filtering and sorting.
    SeniorMedium◆ Commonly asked
    #api#pagination
    PracticeGeeksforGeeks↗Search↗
  • Implement an idempotent "charge" endpoint.
    SeniorHard◆ Commonly asked
    #idempotency#payments
    PracticeGeeksforGeeks↗Search↗
03

Round 03 · 2 questions

System Design

High-level architecture of a large-scale system.

  • Design a file-sharing service with permissions.
    SeniorMedium◆ Commonly asked
    #storage#acl
    PracticeGeeksforGeeks↗Search↗
  • Design a ride-sharing service like Uber.
    SeniorHard◆ Commonly asked
    #geospatial#matching
    PracticeGeeksforGeeks↗Search↗
04

Round 04 · 3 questions

Tech Deep-Dive

Deep questions on your core stack and fundamentals.

  • How do you design an idempotency-key system for payments?
    SeniorHard◆ Commonly asked
    #idempotency#payments
    PracticeGeeksforGeeks↗Search↗
  • Explain the difference between horizontal and vertical scaling.
    SeniorEasy◆ Commonly asked
    #scale
    PracticeGeeksforGeeks↗Search↗
  • Explain eventual consistency with a real example.
    SeniorHard◆ Commonly asked
    #distributed
    PracticeGeeksforGeeks↗Search↗
05

Round 05 · 1 question

Hiring Manager

Scope, ownership, and role-fit discussion with the manager.

  • Where do you want to grow in the next two years?
    Senior◆ Commonly asked
    #growth
06

Round 06 · 2 questions

Behavioral / HR

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

  • Describe a goal you set and how you achieved it.
    Senior◆ Commonly asked
    #ownership#star
  • When did you take ownership of something outside your scope?
    Senior◆ Commonly asked
    #ownership#star

Practice each round across every company

  • DSA / Coding
  • Machine Coding
  • System Design
  • Tech Deep-Dive
  • Hiring Manager
  • 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.