Designing Tiktok

Build a TikTok of your own. TikTok is a short-form, video-sharing app that allows users to create and share 15-second videos, on any topic.

Courtesy of Bytedance

Developing an app that can let users create & share videos could be a cakewalk for many seasoned developers of you, but designing the complete infra of an app with 100 million monthly active users is a different game.



Lets walk through a small story to understand the Logical Design :

X created a lovely Video Sharing App after months of hard work. His 2 friends liked it & started using it.

His friends uploaded daily 2 videos that gets stored on a 10GB Server Space that X bought.

Number of users start increasing once X's app is on TV, a sudden increase of 10,000 users. Server Space soon exhausted & the new users are unable to upload new videos.

X bought more server space, but that too soon exhausted with increasing users.

X realized he need to reduce video size before upload. He wrote a smart code that reduces video size without compromising on video quality. Now clients have to do too much work before upload so X moved this code to its Application Servers.

X bought new Application Servers with high processing powers for quick turnaround time. (Sponsors were attracted).

Another TV ad brought total users to be 1million, things started falling apart, Application Server couldn't reply all of the requests & finally it went down. Users were angry, Sponsors were unhappy.

X realized he needs Replicas of Application Servers such that when one Application Server dies another takes up its place & user has a notion that they are being served by single server . X brought 10 new Application Servers & a Load Balancer that evenly distributed load among the Application Server. Everyone is happy again.

With more Server Replicas in place , each video is being uploaded to all the Application Server which takes a lot of time, X wants the system to be quick & consistent. He decides the app can be eventually consistent by copying the video file to 2/3rd of servers and rest can keep uploading in background. This made the app availability high.

Each Server replica communicates to each other via Network, X designed a wonderful algorithm to make the system Network Failure Tolerant by integrating polling, retries.

As the system scales, more are the components required to handle the load. This story covers the Logical Designing of the app, majorly involving CAP Theorem.