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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

← Perplexity

Mid Backend at Perplexity

BackendMidOutcome unknown◆ Commonly asked· 2025

A mid backend loop. Fast-paced; expect follow-ups that push on depth.

The loop · 5 rounds

01

Round 01 · 3 questions

DSA / Coding

Data structures & algorithms on a whiteboard or shared editor.

  • Word break.
    MidMedium◆ Commonly asked
    #dp#string
    PracticeLeetCode↗GeeksforGeeks↗
  • Pow(x, n).
    MidMedium◆ Commonly asked
    #math#recursion
    PracticeLeetCode↗GeeksforGeeks↗
  • 3Sum.
    MidMedium◆ Commonly asked
    #two-pointers#array
    PracticeLeetCode↗GeeksforGeeks↗
02

Round 02 · 2 questions

Machine Coding

Build a working component or service under time pressure.

  • Build a mini ORM query builder (select/where/join).
    MidHard◆ Commonly asked
    #parsing#sql
    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 a food-delivery order/dispatch model.
    MidHard◆ Commonly asked
    #oop#state-machine
    PracticeGeeksforGeeks↗Search↗
04

Round 04 · 3 questions

Tech Deep-Dive

Deep questions on your core stack and fundamentals.

  • 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↗
  • Explain JWT structure and common pitfalls.
    MidMedium◆ Commonly asked
    #auth#security
    PracticeGeeksforGeeks↗Search↗
05

Round 05 · 2 questions

Behavioral / HR

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

  • How do you get up to speed on an unfamiliar codebase?
    Mid◆ Commonly asked
    #learning
  • Describe handling a tight deadline with competing priorities.
    Mid◆ Commonly asked
    #prioritization#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.