Design a notification service for push, email and SMS, handling about fifty million notifications a day, with spikes during marketing campaigns.
~10 min by voice
How to approach it
This checks whether the candidate can design an asynchronous system with uneven traffic: isolate urgent transactional notifications from mass campaigns, survive failures and limits of external providers, and not send the same message twice.
The interviewer will ask this question and listen. Think out loud and ask for a hint if you need one. When you're done, pause or tap “That's my answer”. In about a minute, your score and the points you covered show up here.