System designMediumsd-g562

Subject SchedulingLevel Entry–Mid~30 minCommon in Distributed systems interviewsIndustries Software development, Technology

Question

Design a reminder/scheduled-task feature for a small to-do app. A user sets a reminder for a task at a specific future time, and when that time arrives the system sends them a notification. Reminders can be minutes or weeks out; volume is modest. Describe how you store scheduled reminders and how the system fires them at the right time.

What a strong answer looks like

Clarify scale and constraints first. Propose a clean component breakdown, then go deep on the hard parts — data model, bottlenecks, consistency, failure modes — and name the trade-offs you are making.

Learn the concepts

Narrate your design

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Run or narrate your approach, then ask the coach.