These are LLD questions of the kind Microsoft actually asks — the patterns reported from Microsoft's AI-engineering rounds, where design trade-offs, scale and failure modes matter as much as definitions. Treat this page as a mock interview: say every answer out loud before revealing it. If one surprises you, the lesson behind it is linked at the bottom.
Microsoft LLD concept questions
Microsoft LLD rounds often ask for a notification system supporting multiple channels (email, SMS, push). Design it.
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What should happen in the notification system above if the SMS provider's API call fails for one user, while sending to nine others via email succeeds fine?
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A notification system needs to build the right NotificationChannel from a user's stored preference string ('email', 'sms', 'push'). What pattern fits, and why?
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How to use this page: Microsoft rarely asks something you've never seen — they ask a standard LLD concept and then push one level deeper ("why?", "what would you do if..."). Master the concept in the LLD course lessons, and the follow-up stops being scary.
Keep practising: SOLID Principles, Strategy Pattern, Design a Parking Lot and UML Diagrams cover what most Microsoft LLD rounds test.