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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

← Fastly

Senior Full-stack at Fastly

Full-stackSeniorOffer◆ Commonly asked· 2025

6-round senior fullstack process. Pragmatic questions — more real-world than pure puzzles.

The loop · 6 rounds

01

Round 01 · 3 questions

DSA / Coding

Data structures & algorithms on a whiteboard or shared editor.

  • 3Sum.
    SeniorMedium◆ Commonly asked
    #two-pointers#array
    PracticeLeetCode↗GeeksforGeeks↗
  • Top K frequent elements.
    SeniorMedium◆ Commonly asked
    #heap#hashmap
    PracticeLeetCode↗GeeksforGeeks↗
  • Binary tree level order traversal.
    SeniorMedium◆ Commonly asked
    #tree#bfs
    PracticeLeetCode↗GeeksforGeeks↗
02

Round 02 · 2 questions

Machine Coding

Build a working component or service under time pressure.

  • Build a nested checkbox tree with indeterminate state.
    SeniorHard◆ Commonly asked
    #react#recursion
    PracticeGeeksforGeeks↗Search↗
  • Build a mini ORM query builder (select/where/join).
    SeniorHard◆ Commonly asked
    #parsing#sql
    PracticeGeeksforGeeks↗Search↗
03

Round 03 · 2 questions

System Design

High-level architecture of a large-scale system.

  • Design a news feed / timeline.
    SeniorHard◆ Commonly asked
    #fanout#ranking#cache
    PracticeGeeksforGeeks↗Search↗
  • Design a real-time fraud-detection pipeline.
    SeniorHard◆ Commonly asked
    #streaming#ml
    PracticeGeeksforGeeks↗Search↗
04

Round 04 · 3 questions

Tech Deep-Dive

Deep questions on your core stack and fundamentals.

  • What is tree shaking and when does it fail?
    SeniorMedium◆ Commonly asked
    #bundling
    PracticeGeeksforGeeks↗Search↗
  • Explain hydration and the cost of client vs server rendering.
    SeniorHard◆ Commonly asked
    #ssr#perf
    PracticeGeeksforGeeks↗Search↗
  • Explain memoization: useMemo, useCallback and React.memo.
    SeniorMedium◆ Commonly asked
    #react#perf
    PracticeGeeksforGeeks↗Search↗
05

Round 05 · 1 question

Hiring Manager

Scope, ownership, and role-fit discussion with the manager.

  • How do you grow junior engineers on your team?
    Senior◆ Commonly asked
    #mentorship#leadership
06

Round 06 · 2 questions

Behavioral / HR

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

  • Tell me about a time you went above and beyond for a customer.
    Senior◆ Commonly asked
    #customer#star
  • Tell me about a time you had to learn something quickly.
    Senior◆ Commonly asked
    #learning#star

Practice each round across every company

  • DSA / Coding
  • Machine Coding
  • System Design
  • Tech Deep-Dive
  • Hiring Manager
  • 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.