Design YouTube

In this mock system design interview, Hozefa (Wealthfront EM) answers the interview question, "Design YouTube or a YouTube like service."

Key Concepts:

Reliable and Resilient Infrastructure: A video streaming service must be highly available and resilient to failures to ensure a seamless viewing experience for users.

Load Balancing: Load balancing is important for ensuring that incoming requests are distributed evenly across available resources, allowing for efficient processing of large amounts of video data.

Building Distributed Systems: Distributed architectures, messaging protocols, and consistency models are important for building a scalable and reliable video streaming service.

Efficient Video Streaming

YouTube-like systems need to serve both content creators and viewers. Creators should be able to upload videos from any device, and the system should process them. Viewers should be able to watch videos on any device.

Non-Functional Requirements

For non-functional requirements, the system must be highly available. It should prioritize reads over writes.

Content Creation

To help creators, the system should have an API for uploading video metadata and the video itself.

Large videos can be uploaded through an open socket connection. The system can use a queueing system to process videos into different formats and resolutions.

Videos can be stored in a relational database and blob storage, like S3. The system can split the databases by creator to scale it.

Content Consumption

Viewers can use a streaming service with a Content Delivery Network (CDN) that checks the database to validate permissions and retrieves the video from the blob storage. The system can partition videos by creator.

An adaptive bitrate system can adjust streaming quality based on the viewer's connection speed. An in-memory cache can be used to prevent overload during high-traffic periods, and an invalidation strategy can be used to remove outdated videos from the CDN.

For analytics, a stream or analytics system can be set up.

Improvements

One suggestion for improving the design is to add more fault tolerance measures, such as a master-safe slave configuration for the database.

Additionally, space and cost optimization should be considered, especially for a data-heavy system like a video streaming service.