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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

← American Express

Senior Backend at American Express

BackendSeniorRejected◆ Commonly asked· 2024

A senior backend loop. Fast-paced; expect follow-ups that push on depth.

The loop · 6 rounds

01

Round 01 · 3 questions

DSA / Coding

Data structures & algorithms on a whiteboard or shared editor.

  • Implement a trie (prefix tree).
    SeniorMedium◆ Commonly asked
    #trie
    PracticeLeetCode↗GeeksforGeeks↗
  • Coin change — fewest coins to make an amount.
    SeniorMedium◆ Commonly asked
    #dp
    PracticeLeetCode↗GeeksforGeeks↗
  • Course Schedule — detect a cycle / topological sort.
    SeniorMedium◆ Commonly asked
    #graph#topo-sort
    PracticeLeetCode↗GeeksforGeeks↗
02

Round 02 · 2 questions

Machine Coding

Build a working component or service under time pressure.

  • Build a file-upload service with chunking and resume.
    SeniorHard◆ Commonly asked
    #streaming#storage
    PracticeGeeksforGeeks↗Search↗
  • Build auth middleware that verifies a JWT.
    SeniorMedium◆ Commonly asked
    #auth#security
    PracticeGeeksforGeeks↗Search↗
03

Round 03 · 2 questions

System Design

High-level architecture of a large-scale system.

  • Design a file-sharing service with permissions.
    SeniorMedium◆ Commonly asked
    #storage#acl
    PracticeGeeksforGeeks↗Search↗
  • Design a content delivery network (CDN).
    SeniorHard◆ Commonly asked
    #cdn#cache#edge
    PracticeGeeksforGeeks↗Search↗
04

Round 04 · 3 questions

Tech Deep-Dive

Deep questions on your core stack and fundamentals.

  • How do you run a zero-downtime database migration?
    SeniorHard◆ Commonly asked
    #databases
    PracticeGeeksforGeeks↗Search↗
  • Compare rate-limiting algorithms and their trade-offs.
    SeniorMedium◆ Commonly asked
    #rate-limit
    PracticeGeeksforGeeks↗Search↗
  • Idempotency in APIs — why and how.
    SeniorMedium◆ Commonly asked
    #api-design#idempotency
    PracticeGeeksforGeeks↗Search↗
05

Round 05 · 1 question

Hiring Manager

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

  • How do you run an incident and the postmortem after?
    Senior◆ Commonly asked
    #reliability#process
06

Round 06 · 2 questions

Behavioral / HR

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

  • Tell me about a time you simplified something overly complex.
    Senior◆ Commonly asked
    #judgment#star
  • When did you take ownership of something outside your scope?
    Senior◆ Commonly asked
    #ownership#star

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