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Reels / Shorts — Notes#

Functional#

  • Short vertical video (15–90 s).
  • Sound library (use existing audio).
  • Vertical "For You"-style feed.
  • Like, share, save, remix.
  • Shopping / tagged products.

Non-functional#

  • p99 next-video first frame < 100 ms (because prefetched).
  • 100M+ videos uploaded daily across Meta/Google.
  • 1B+ DAU.

Capacity#

  • Similar to TikTok: many PB/yr storage; trillions of impressions/yr.

Schema#

  • videos(id, owner, audio_id, ts, duration_ms, ladders[], region)
  • events(user, video, ts, action, watch_ms) Kafka
  • audio_library(id, isrc, owner_artist, license)

Trade-offs#

  • Tightly coupled to a parent platform (Instagram, YouTube): leverage shared infra (auth, CDN, ranker).
  • Prefetch policy = the difference between feel of "instant" vs "laggy".
  • Music licensing more aggressive enforcement than long-form.

Refs#

  • Instagram Reels engineering posts, YouTube Shorts launches, TikTok recommendation paper "Monolith", ByteByteGo "Design TikTok / Reels".