Chat System Design (1-on-1)

System DesignAnthropicLast reported August 2026Medium Frequency

Reported: 7× across candidate reports
First seen: November 2025
Last reported: August 2026
Also asked in: Phone Screen
Reported outcome: mixed

Problem Overview

Design a scalable real-time one-to-one (1:1) chat system. Only single-device (web) usage needs to be supported; group chat, channels, and multi-device sync are explicitly out of scope. The design must address: (1) real-time message delivery between two users; (2) offline message queuing and delivery when the recipient comes back online;…

6 candidate-reported follow-ups — the exact probes interviewers asked, with the trigger for each
The rest of the problem statement — full requirements, constraints, and edge cases
Approach and trade-offs — what passing candidates did, and the mistakes that sink people

Unlock the full Anthropic catalog

Full problem statements, candidate-reported follow-ups, and walkthroughs — for every Anthropic question.

Unlock with Pro

Already a member? Sign in

Verified Source

Every question is reconstructed from multiple independent candidate reports. Verbatim follow-ups, not invented ones.

Codex Fact-Checked

Technical claims, formulas, and scale numbers are reviewed against primary sources.

Interviewer Follow-ups

The exact follow-ups reported by candidates, with the trigger that prompts each one — plus the mistakes that sink people.