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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

← PlanetScale

Senior Backend at PlanetScale

BackendSeniorOutcome unknown◆ Commonly asked· 2025

Senior backend interview. 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.

  • Maximum depth of a binary tree.
    SeniorEasy◆ Commonly asked
    #tree#dfs
    PracticeLeetCode↗GeeksforGeeks↗
  • House robber.
    SeniorMedium◆ Commonly asked
    #dp
    PracticeLeetCode↗GeeksforGeeks↗
  • House robber II.
    SeniorMedium◆ Commonly asked
    #dp
    PracticeLeetCode↗GeeksforGeeks↗
02

Round 02 · 2 questions

Machine Coding

Build a working component or service under time pressure.

  • Implement an LRU + TTL cache library.
    SeniorHard◆ Commonly asked
    #cache#ttl
    PracticeGeeksforGeeks↗Search↗
  • Parse and evaluate a simple expression/DSL.
    SeniorMedium◆ Commonly asked
    #parsing
    PracticeGeeksforGeeks↗Search↗
03

Round 03 · 2 questions

System Design

High-level architecture of a large-scale system.

  • Design a leaderboard for millions of players.
    SeniorMedium◆ Commonly asked
    #redis#ranking
    PracticeGeeksforGeeks↗Search↗
  • Design a news feed / timeline.
    SeniorHard◆ Commonly asked
    #fanout#ranking#cache
    PracticeGeeksforGeeks↗Search↗
04

Round 04 · 3 questions

Tech Deep-Dive

Deep questions on your core stack and fundamentals.

  • Explain optimistic vs pessimistic locking.
    SeniorHard◆ Commonly asked
    #databases
    PracticeGeeksforGeeks↗Search↗
  • How does a bloom filter work and when would you use one?
    SeniorMedium◆ Commonly asked
    #data-structures#probabilistic
    PracticeGeeksforGeeks↗Search↗
  • How do you retry without amplifying load?
    SeniorHard◆ Commonly asked
    #reliability
    PracticeGeeksforGeeks↗Search↗
05

Round 05 · 1 question

Hiring Manager

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

  • Tell me about a technical bet that did not pay off.
    Senior◆ Commonly asked
    #risk#judgment
06

Round 06 · 2 questions

Behavioral / HR

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

  • Describe working with an ambiguous or shifting requirement.
    Senior◆ Commonly asked
    #ambiguity#star
  • Describe a time you improved a process or tool for your team.
    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.