Design a wearable health monitoring system
PremiumIoT systemMedium
- BLE
- Store and forward
- Battery budget
Quick answer
This ioT system interview question asks you to design a wearable health monitoring system. Aim for a design that collects data from many devices and acts on it reliably, then explain device connections, ingestion, storage and trade-offs. Interviewers want to see how you handle unreliable networks, device scale and data volume.
The problem
Design a wearable health monitoring system: a wrist band that tracks heart rate, blood oxygen, steps and falls, syncs over BLE through a phone app, and alerts caregivers. The hard parts are a five-day battery, a phone that is not always nearby, and alerts that must not be late or lost.
The band has no cellular or Wi-Fi radio. It talks only to the owner's phone over BLE, and the phone app uploads to the cloud. Older users share their data with family caregivers and, if they choose, with a doctor.
What must a wearable health monitoring system do?
- Continuous metrics: Heart rate every second while worn, blood oxygen every 10 minutes at night, and steps.
- Fall alerts: A detected fall that the wearer does not cancel within 30 seconds alerts caregivers within 60 seconds.
How well must it do it?
- Battery: At least 5 days on a 300 mAh battery with normal use.
- No lost data: Readings are deleted from the band only after the cloud confirms they are stored.
What scale should you design for?
Use these numbers in your estimates.
The scale numbers unlock with this questionUnlock
Key concepts
- BLE
- Store and forward
- Battery budget
- Health alerts
- Time series
- Phone gateway
How you’ll practise
- Requirements
- Estimate
- Device and connectivity
- Ingestion and processing
- Device management and updates
- Wrap-up
Lala, personalized to you, gives a hint when you ask and reviews your design when you are ready.
What do interviewers look for?
In any IoT system design round.
- Clarifies device count, message rate and payload size
- Handles devices that go offline and reconnect
- Plans ingestion that absorbs bursts
- Separates hot real-time data from long-term storage
- Covers device identity, updates and security
- Explains what runs on the device and what runs in the cloud
Questions people ask about this interview question
- Which design type is this question?
- It is an ioT system question. You design a wearable health monitoring system and explain your choices the way you would in an interview.
- Is this question asked at entry level?
- It is marked Medium. Entry-level engineers can practise it, but it expects you to reason about requirements and trade-offs, not only list components.
- What should I cover first?
- Start with the devices, what they send, how often and what must happen with it. Agree on scope with the interviewer before you design anything.
- Can I practise it for free?
- It is a premium question. Sign up and unlock it once for 10 credits; it then stays unlocked. When you finish, Lala, your personalized AI mentor, can review your design for 30 credits.
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Updated · Written by the SevyDevy team