Hard Design: Social Media Platform (Instagram)

What technique prevents the same user from liking a photo multiple times?

— Tests your understanding of this concept.

Answer Options

A Database unique constraint on (user_id, post_id)

B Redis SET membership check before incrementing counter

C Rate limiting per user

D Both A and B are valid approaches

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This question is from the Design: Social Media Platform (Instagram) topic (System Design Cases).

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