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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

← Vercel

Mid Backend at Vercel

BackendMidOffer◆ Commonly asked· 2025

5-round mid backend process. Coding-heavy early, design and behavioral later.

The loop · 5 rounds

01

Round 01 · 3 questions

DSA / Coding

Data structures & algorithms on a whiteboard or shared editor.

  • Implement a trie (prefix tree).
    MidMedium◆ Commonly asked
    #trie
    PracticeLeetCode↗GeeksforGeeks↗
  • Validate a binary search tree.
    MidMedium◆ Commonly asked
    #tree#dfs
    PracticeLeetCode↗GeeksforGeeks↗
  • Combination sum.
    MidMedium◆ Commonly asked
    #backtracking
    PracticeLeetCode↗GeeksforGeeks↗
02

Round 02 · 2 questions

Machine Coding

Build a working component or service under time pressure.

  • Implement a token-bucket rate limiter as a service.
    MidMedium◆ Commonly asked
    #rate-limit
    PracticeGeeksforGeeks↗Search↗
  • Build a webhook receiver with signature verification.
    MidMedium◆ Commonly asked
    #security#api
    PracticeGeeksforGeeks↗Search↗
03

Round 03 · 1 question

Low-Level Design

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

  • Design an elevator control system.
    MidMedium◆ Commonly asked
    #oop#state-machine
    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.
    MidHard◆ Commonly asked
    #concurrency
    PracticeGeeksforGeeks↗Search↗
  • How do you prevent and detect N+1 queries?
    MidMedium◆ Commonly asked
    #databases#orm
    PracticeGeeksforGeeks↗Search↗
  • Compare rate-limiting algorithms and their trade-offs.
    MidMedium◆ Commonly asked
    #rate-limit
    PracticeGeeksforGeeks↗Search↗
05

Round 05 · 2 questions

Behavioral / HR

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

  • How do you handle competing priorities from two managers?
    Mid◆ Commonly asked
    #prioritization#star
  • Describe a goal you set and how you achieved it.
    Mid◆ Commonly asked
    #ownership#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.