Database Scaling for Notification System

System DesignOpenAILast reported October 2025Low Frequency

Reported: 1× across candidate reports
First seen: October 2025
Last reported: October 2025
Reported outcome: unknown

Problem Overview

Design Slack with a focus on two major challenges: (1) Large channel fan-out — how to efficiently deliver messages to all members of a large channel; (2) Notification system — how notifications for unread messages and offline push notifications…

3 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.