Home-feed delivery at scale

Design the home-feed delivery for a creator platform where most users follow 100–500 creators, but a small number of mega-creators have 50M+ followers and post several times a day. Feeds must load in under 300ms and show new posts within seconds for normal accounts. Decide between fan-out-on-write and fan-out-on-read, justify the hybrid, and explain how you handle the mega-creator post storm without melting the write path.