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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.

MIT · © 2026

← Datadog

New Grad / Junior Backend at Datadog

BackendNew Grad / JuniorOffer◆ Commonly asked· 2024

5-round junior backend process. 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.

  • Group items by frequency and return the top K.
    New Grad / JuniorMedium◆ Commonly asked
    #hashmap#heap
    PracticeGeeksforGeeks↗Search↗
02

Round 02 · 3 questions

DSA / Coding

Data structures & algorithms on a whiteboard or shared editor.

  • Find minimum in rotated sorted array.
    New Grad / JuniorMedium◆ Commonly asked
    #binary-search
    PracticeLeetCode↗GeeksforGeeks↗
  • Permutations.
    New Grad / JuniorMedium◆ Commonly asked
    #backtracking
    PracticeLeetCode↗GeeksforGeeks↗
  • Lowest common ancestor of a binary tree.
    New Grad / JuniorMedium◆ Commonly asked
    #tree
    PracticeLeetCode↗GeeksforGeeks↗
03

Round 03 · 2 questions

Machine Coding

Build a working component or service under time pressure.

  • Implement an LRU + TTL cache library.
    New Grad / JuniorHard◆ Commonly asked
    #cache#ttl
    PracticeGeeksforGeeks↗Search↗
  • Build a mini ORM query builder (select/where/join).
    New Grad / JuniorHard◆ Commonly asked
    #parsing#sql
    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?
    New Grad / JuniorMedium◆ Commonly asked
    #api-design
    PracticeGeeksforGeeks↗Search↗
  • How do circuit breakers and bulkheads improve resilience?
    New Grad / JuniorMedium◆ Commonly asked
    #reliability
    PracticeGeeksforGeeks↗Search↗
  • How do you design a schema for a multi-currency ledger?
    New Grad / JuniorHard◆ Commonly asked
    #databases#money
    PracticeGeeksforGeeks↗Search↗
05

Round 05 · 2 questions

Behavioral / HR

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

  • Tell me about a time you simplified something overly complex.
    New Grad / Junior◆ Commonly asked
    #judgment#star
  • Tell me about the hardest bug you have debugged.
    New Grad / Junior◆ Commonly asked
    #debugging#star

◆ This experience is composed from commonly reported questions for this role and level. Real, individually-shared interviews will be layered in over time.