fan_out_on_write introduces risk fanout

fan out on writeIntroduces Riskfanout amplification

Source: Pattern·Target: Failure Mode

Summary

Fan-out on write multiplies each post event into one write per follower; at high follower counts this produces write amplification that can saturate the write path for popular accounts.

Evidence

·fanout_amplification lists fan_out_on_write in affects_patterns; a 100k-follower post triggers 100k cache writes (failure_modes/fanout_amplification.yaml)
·fan_out_on_write's write-amplification tradeoff: one post write becomes N cache writes where N=follower count (patterns/fan_out_on_write.yaml tradeoffs)

Evidence grounding

Grounded, 2 supporting items

One post by a high-follower account multiplies into N cache writes.