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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

← Costco

New Grad / Junior Backend at Costco

BackendNew Grad / JuniorOffer◆ Commonly asked· 2025

Junior backend interview. Fundamentals mattered as much as getting to an answer.

The loop · 5 rounds

01

Round 01 · 1 question

Online Assessment

Timed online coding / aptitude screen, usually the first filter.

  • Aptitude and logical-reasoning section.
    New Grad / JuniorEasy◆ Commonly asked
    #aptitude
    PracticeGeeksforGeeks↗Search↗
02

Round 02 · 3 questions

DSA / Coding

Data structures & algorithms on a whiteboard or shared editor.

  • Insert interval.
    New Grad / JuniorMedium◆ Commonly asked
    #intervals
    PracticeLeetCode↗GeeksforGeeks↗
  • Valid anagram.
    New Grad / JuniorEasy◆ Commonly asked
    #string#hashmap
    PracticeLeetCode↗GeeksforGeeks↗
  • Trapping rain water.
    New Grad / JuniorHard◆ Commonly asked
    #two-pointers#array
    PracticeLeetCode↗GeeksforGeeks↗
03

Round 03 · 2 questions

Machine Coding

Build a working component or service under time pressure.

  • Implement a job queue with retries and backoff.
    New Grad / JuniorHard◆ Commonly asked
    #queue#reliability
    PracticeGeeksforGeeks↗Search↗
  • Design and build a URL-shortener service (API + storage).
    New Grad / JuniorMedium◆ Commonly asked
    #api#hashing
    PracticeGeeksforGeeks↗Search↗
04

Round 04 · 3 questions

Tech Deep-Dive

Deep questions on your core stack and fundamentals.

  • Explain how you handle concurrency / race conditions.
    New Grad / JuniorHard◆ Commonly asked
    #concurrency
    PracticeGeeksforGeeks↗Search↗
  • How would you design and version a public REST API?
    New Grad / JuniorMedium◆ Commonly asked
    #api-design
    PracticeGeeksforGeeks↗Search↗
  • ACID vs BASE and transaction isolation levels.
    New Grad / JuniorHard◆ Commonly asked
    #databases#transactions
    PracticeGeeksforGeeks↗Search↗
05

Round 05 · 2 questions

Behavioral / HR

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

  • Describe a disagreement on a code review and how it ended.
    New Grad / Junior◆ Commonly asked
    #conflict#star
  • Tell me about receiving hard feedback and acting on it.
    New Grad / Junior◆ Commonly asked
    #feedback#star

Practice each round across every company

  • Online Assessment
  • DSA / Coding
  • Machine Coding
  • 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.