Netflix's system design

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Netflix · system design

Netflix is two systems: a brain on AWS that decides what you can watch and where it should come from, and its own CDN that hands you the video from inside your internet provider.

+ The whole system in one paragraph

Netflix is split in two. Everything except the video (sign-in, browsing, recommendations, picking which server streams to you) runs on Amazon's cloud, AWS. The video itself comes from Netflix's own servers inside internet providers, filled every night with what people are predicted to watch. Your player pulls it in small chunks, changing quality as your connection changes.

325M+
paid memberships (Q4 2025)[17]
65M
concurrent streams at the peak — Paul vs Tyson, Nov 2024[18]
14,000+
Open Connect servers, in 142 countries (2020 data)[3]

In this lesson

4 chapters · ~8 min · a quick check in each

Everything is on this page — just scroll down ↓

Chapter 1 of 4

The whole system

1
Requirements

What it must do — and how well

What Netflix must do (yellow) and how well it must do it (blue). Every box that follows exists to meet one of them. The '1,000+ kinds of devices' and 99.99% goal date from 2013.

ⓘ Details & sources

Yellow = what the system must do. Blue = how well it must do it.[24][11]

Start playing faston 1,000+ kinds ofdevices.Never stop mid-show:change qualityinstead ofbuffering.Keep nearly thewhole catalog closeto every viewer.Remember everyprofile, every'continue watching'.Internalavailability goal:99.99%.Lose a whole AWSregion — and nobodynotices.Every gigabytecheaper than lastyear.Live: millionsjoining in the sameminute.
2
Architecture

The two halves of Netflix

The left half runs on AWS (three regions since 2016) and makes every decision: who you are, what you may watch, which server sends it. The right half: Netflix's own video servers (OCAs).

ⓘ Details & sources

Left: the brain, on AWS. Right: the video, on Netflix's own servers. Click any piece; play a flow.[1][2][36]

Watch it happen:
Control plane — AWS, 3 regionsOpen Connect — the video12344on a missfillpeer fillreportsthe video, from close by5Your deviceTV, phone, laptopEdge gatewayZuulAPI layerGraphQLPlayback appsauth + licensingSteeringpicks your OCAsCache controlwho holds whatEVCachein memory, ~1 msCassandramember dataOrigin (S3)every encoded fileOCAs at exchangespeering pointsOCAs inside ISPsfree hardware, ISP hosts
clientedge / CDNload balancerservicecachedatabasestorage dashed border = simplified model
12345
Step 1 of 5

You press play. The request goes to Netflix's cloud on AWS, through the edge gateway.

Quick check

Netflix's front door handled 1M+ requests a second (2018). About how many requests a day is that?

Pick one — or just keep scrolling, it's not graded.

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  1. 2Streaming the video
  2. 3Your home page
  3. 4Failures & growth
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