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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

← Character.AI

Senior Backend at Character.AI

BackendSeniorOffer◆ Commonly asked· 2024

Senior backend interview. Fundamentals mattered as much as getting to an answer.

The loop · 6 rounds

01

Round 01 · 3 questions

DSA / Coding

Data structures & algorithms on a whiteboard or shared editor.

  • Sliding window maximum.
    SeniorHard◆ Commonly asked
    #deque#sliding-window
    PracticeLeetCode↗GeeksforGeeks↗
  • Regular expression matching.
    SeniorHard◆ Commonly asked
    #dp#string
    PracticeLeetCode↗GeeksforGeeks↗
  • Construct binary tree from preorder and inorder traversal.
    SeniorMedium◆ Commonly asked
    #tree#recursion
    PracticeLeetCode↗GeeksforGeeks↗
02

Round 02 · 2 questions

Machine Coding

Build a working component or service under time pressure.

  • Design and build a URL-shortener service (API + storage).
    SeniorMedium◆ Commonly asked
    #api#hashing
    PracticeGeeksforGeeks↗Search↗
  • Build a REST endpoint with pagination, filtering and sorting.
    SeniorMedium◆ Commonly asked
    #api#pagination
    PracticeGeeksforGeeks↗Search↗
03

Round 03 · 2 questions

System Design

High-level architecture of a large-scale system.

  • Design a search indexing pipeline (crawl to index to serve).
    SeniorHard◆ Commonly asked
    #indexing#pipeline
    PracticeGeeksforGeeks↗Search↗
  • Design a chat application like WhatsApp.
    SeniorHard◆ Commonly asked
    #websocket#fanout#storage
    PracticeGeeksforGeeks↗Search↗
04

Round 04 · 3 questions

Tech Deep-Dive

Deep questions on your core stack and fundamentals.

  • What is a deadlock and how do you avoid one?
    SeniorHard◆ Commonly asked
    #concurrency
    PracticeGeeksforGeeks↗Search↗
  • Message queues vs pub/sub — when to use each.
    SeniorMedium◆ Commonly asked
    #messaging
    PracticeGeeksforGeeks↗Search↗
  • How do you design a schema for a multi-currency ledger?
    SeniorHard◆ Commonly asked
    #databases#money
    PracticeGeeksforGeeks↗Search↗
05

Round 05 · 1 question

Hiring Manager

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

  • What would your first 90 days here look like?
    Senior◆ Commonly asked
    #planning
06

Round 06 · 2 questions

Behavioral / HR

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

  • Tell me about a time you had to say no to a stakeholder.
    Senior◆ Commonly asked
    #influence#star
  • Describe working with an ambiguous or shifting requirement.
    Senior◆ Commonly asked
    #ambiguity#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.