Hard Design: Social Media Platform (Instagram)

How is the like count for a photo stored and retrieved at 49,000 likes/sec?

— Tests your understanding of this concept.

Answer Options

A Directly in SQL posts table, updated per like

B Redis INCR for fast atomic increment, batch-written to SQL DB every 5 seconds

C Counted by querying likes table at read time

D Stored in Elasticsearch for fast aggregation

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

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