Design the Instagram feed

Intermediate70 minBuilds News FeedRead first: 7.2 Read and write patterns, 7.4 When caches fail, 10.1 Why queues

STEP 1 OF 13

The brief

You are designing the home feed of a photo-sharing app like Instagram. People follow other accounts; when they open the app, they see recent posts from the accounts they follow, newest or best first, and can scroll back further.

How big it is

Feed loads: 50,000 / second at peak
New posts: 1,000 / second
Average followers per account: about 300
Largest accounts: hundreds of millions of followers
p99 goal: under 200 ms for a feed page

What makes feeds hard

Reads dwarf writes, 50 to 1. Whatever the feed costs to build, it must be cheap to read.
A post goes to many feeds. One post from an account with 300 followers lands in 300 timelines; one from a celebrity lands in 300 million.
Freshness is flexible. A post appearing in followers' feeds a few seconds late is fine. A feed taking two seconds to load is not.

Media (the photos themselves) is served from object storage through a CDN, as in the blob storage module. This lab is about the feed: which post ids each user sees, in what order.

All changes saved

0 components · 0 connections

A blank canvas. A better system.

Add components from the palette, then drag between them to connect the request and event flow.

React Flow

Design the Instagram feed

Intermediate70 minBuilds News FeedRead first: 7.2 Read and write patterns, 7.4 When caches fail, 10.1 Why queues

STEP 1 OF 13

The brief

How big it is

Feed loads: 50,000 / second at peak
New posts: 1,000 / second
Average followers per account: about 300
Largest accounts: hundreds of millions of followers
p99 goal: under 200 ms for a feed page

What makes feeds hard

Reads dwarf writes, 50 to 1. Whatever the feed costs to build, it must be cheap to read.
A post goes to many feeds. One post from an account with 300 followers lands in 300 timelines; one from a celebrity lands in 300 million.
Freshness is flexible. A post appearing in followers' feeds a few seconds late is fine. A feed taking two seconds to load is not.

Media (the photos themselves) is served from object storage through a CDN, as in the blob storage module. This lab is about the feed: which post ids each user sees, in what order.

All changes saved

0 components · 0 connections

A blank canvas. A better system.

Add components from the palette, then drag between them to connect the request and event flow.

React Flow