Feeds are built by fan-out on write. A celebrity with 50 million followers posts. What do large feed systems do?

Options

• ✗ Write the post into all 50 million feeds as fast as possible
• ✓ Skip fan-out for celebrities and merge their recent posts into each feed when it is read Correct
• ✗ Shard the celebrity's followers across more queues
• ✗ Rate-limit how often celebrities may post

Why

This hybrid keeps fan-out on write for ordinary accounts (fast reads) and fan-out on read for the few huge ones, which would otherwise create tens of millions of writes per post.

Review this in your daily deck → All cards in Queues