Status: IN
The hybrid fan-out strategy bounds both paths: the follower-count threshold limits write amplification to non-celebrity authors, and heap-merge limits read cost to O(k log n) for pull-based celebrity retrieval.
Threshold caps write fan-out; heap merge caps read materialization — each path has an independent cost bound
Depends on (SL): news-feed-hybrid-splits-on-follower-count, news-feed-pull-uses-heap-merge