System Design: ChatGPT / GPT Interactive Chat UI

System DesignOpenAILast reported July 2026High Frequency
Reported
22× across candidate reports
First seen
July 2025
Last reported
July 2026
Reported outcome
mixed

Problem Overview

Design a ChatGPT-like interactive chat system end-to-end. The scope varies by role (frontend/fullstack/backend/mobile) and interviewer background, but common requirements include: 1. Core chat functionality: User sends a message/prompt; the AI model returns a response streamed token-by-token to the client in real time. 2. Streaming: Implement server-sent events (SSE) or WebSocket…

  • 9 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
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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.
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