Design third-party feature alerts for alexa
PremiumBackend systemMedium
- Notification fan out
- Audience targeting
- Offline delivery
Quick answer
This backend system interview question asks you to design third-party feature alerts for alexa. Aim for a design that meets its requirements at the stated scale, then explain its main components, data flow and trade-offs. Interviewers want to see how you scope the problem, size it and defend each choice.
The problem
Design third-party feature alerts for Alexa-style voice assistants: tell users about a new third-party skill or feature on their smart speakers and displays. The system picks who should hear it, fans out to millions of devices, waits for offline ones and falls back to phone push or email, while respecting quiet hours and never alerting twice.
A partner launches a new recipe skill and wants owners of kitchen displays in the US and UK who use cooking skills to hear about it. A device shows a light-ring notification and the user hears the alert when they ask for their notifications. Partners submit campaigns, a reviewer approves them, and the platform caps how often users get them.
What must the system do?
- Targeting: Select accounts by locale, device type and skill usage, excluding anyone who opted out of feature alerts.
- Delivery with fallback: Deliver to the account’s devices; if every device stays offline for 72 hours, send one phone push, or one email if there is no app.
How well must it do it?
- No duplicates: Retries and crashes never create a second alert or a second fallback for the same account and campaign.
- Gateway budget: Alert traffic stays under 10,000 device messages per second so it never slows normal device traffic.
What scale should you design for?
Use these numbers in your estimates.
The scale numbers unlock with this questionUnlock
Key concepts
- Notification fan out
- Audience targeting
- Offline delivery
- Idempotency keys
- Quiet hours
- Frequency capping
How you’ll practise
- Requirements
- Estimate
- API and data
- High-level design
- Deep dives
- 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 backend system design round.
- Clarifies the requirements before drawing anything
- Uses a few numbers that actually change the design
- Draws a clear path from the client to storage
- Picks storage and caching with reasons, not by habit
- Explains what breaks first under load and how to fix it
- States trade-offs openly instead of claiming a perfect design
Questions people ask about this interview question
- Which design type is this question?
- It is a backend system question. You design third-party feature alerts for alexa 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 requirements: what the system must do, how well it must do it and which numbers change the design. 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