Twitch / Live Streaming — Notes

Functional

• Live ingest from streamers; transcode + ABR delivery.
• Real-time chat with mods + bot ecosystem.
• VOD recording and clips.
• Subscriptions, bits, ads.
• Channel discovery + recommendations.

Non-functional

• Glass-to-glass latency 2–5 s (LL-HLS) or sub-second (WebRTC paths).
• Concurrent streams: 100k+ live.
• Concurrent viewers: 10M+ on big events.
• 99.9% ingest availability.

Capacity

• Each streamer ingest: 6–10 Mbps × 100k streams = 1 Tbps ingest.
• Egress at peak: tens of Tbps.
• VOD storage: hundreds of PB.

Schema

• streams(channel_id, started_at, ingest_node, encodes[], status)
• chat_messages(channel_id, user_id, ts, text, flags) (transient + archive)
• vods(id, channel_id, started_at, duration, segments[])
• clips(id, vod_id, start, end, creator_id)

Trade-offs

• Cloud + own POPs: own POPs near gaming PoPs reduce streamer latency.
• Latency vs reliability: lower latency = smaller buffers = more rebuffering.
• Per-stream transcoding is the dominant cost; not every stream gets full ladder (low-viewer streams stay source-only).

Refs

• Twitch engineering blog (Mixer, live transcoding, chat at scale), Amazon Interactive Video Service (IVS) docs, YouTube Live papers, "Low-Latency HLS" Apple spec, ByteByteGo "Design live streaming".