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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

Mid Full-stack at Costco

Full-stackMidOffer◆ Commonly asked· 2025

5-round mid fullstack process. Balanced across coding, design, and collaboration.

The loop · 5 rounds

01

Round 01 · 3 questions

DSA / Coding

Data structures & algorithms on a whiteboard or shared editor.

  • Kth smallest element in a BST.
    MidMedium◆ Commonly asked
    #tree#bst
    PracticeLeetCode↗GeeksforGeeks↗
  • LRU cache with O(1) get and put.
    MidMedium◆ Commonly asked
    #hashmap#linked-list
    PracticeLeetCode↗GeeksforGeeks↗
  • Longest increasing subsequence.
    MidHard◆ Commonly asked
    #dp#binary-search
    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 auth middleware that verifies a JWT.
    MidMedium◆ Commonly asked
    #auth#security
    PracticeGeeksforGeeks↗Search↗
03

Round 03 · 1 question

Low-Level Design

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

  • Design a movie-ticket booking system (BookMyShow).
    MidHard◆ Commonly asked
    #oop#concurrency
    PracticeGeeksforGeeks↗Search↗
04

Round 04 · 3 questions

Tech Deep-Dive

Deep questions on your core stack and fundamentals.

  • How do you design a public API for backward compatibility?
    MidMedium◆ Commonly asked
    #api-design
    PracticeGeeksforGeeks↗Search↗
  • How do you code-split and lazy-load a route?
    MidMedium◆ Commonly asked
    #bundling#perf
    PracticeGeeksforGeeks↗Search↗
  • Trade-offs of gRPC vs REST vs GraphQL.
    MidMedium◆ Commonly asked
    #api-design
    PracticeGeeksforGeeks↗Search↗
05

Round 05 · 2 questions

Behavioral / HR

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

  • When did you have to make a decision with incomplete data?
    Mid◆ Commonly asked
    #judgment#star
  • How do you handle competing priorities from two managers?
    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.