How Notion Cut Latency by 20% with Caching

Summary

In this video, the presenter excitedly discusses a break from coding to delve into system design, with a special announcement about a new free newsletter covering coding interviews, system design, and tech news. The focus is on how Notion uses SQLite for local caching, enhancing page load and navigation speeds by reducing reliance on network requests. The video explores the technicalities of SQLite, its use in browsers via WebAssembly, and the implementation of web workers for efficient, non-blocking I/O operations. The presenter also addresses performance optimizations, data corruption issues due to concurrent writes, and the importance of ACID compliance in databases.

Takeaways

• 🎉 The speaker is excited to discuss system design and introduces a new newsletter focused on coding, interviews, system design, career advice, and tech news.
• 📑 Subscribers to the newsletter gain access to a 500-page system design PDF and upcoming algorithm animations and lessons.
• 🛠 The video deep-dives into how Notion uses SQLite for caching, emphasizing the hands-on approach with coding examples and diagrams.
• 📊 Notion's use of caching via SQLite reduces load times by about 20%, showcasing the impact of efficient caching strategies.
• 🤔 The video contrasts SQLite with traditional databases like PostgreSQL and MongoDB, highlighting its lightweight nature and local storage capabilities.
• 📱 The discussion includes the use of WebAssembly to enable browsers to run code like SQLite, which is crucial for local caching.
• 🔧 A practical demonstration of Web Workers is provided, illustrating how they can run SQLite operations in a separate thread for better performance.
• 🏎 Notion's strategy of racing file system reads against network requests ensures the fastest data retrieval for users.
• 🔒 The video addresses data corruption issues caused by concurrent writes to the cache and how Notion resolved them with a shared Web Worker.
• 📝 The speaker emphasizes the importance of understanding the details behind system design decisions, such as the use of ACID-compliant databases and the role of the browser's file system API.

Q & A

What is the main topic of the video script?

The main topic of the video script is about system design, specifically focusing on how Notion uses SQLite for caching in the browser.

What is the purpose of the speaker's new newsletter?

The purpose of the speaker's new newsletter is to provide coding interview prep, system design advice, career advice, tech news, and other resources, including a 500-page system design PDF and algorithm animations.

Why did Notion choose SQLite over local storage for caching?

Notion chose SQLite over local storage for caching because local storage has limitations on the amount of data it can store and writing to it is not as efficient as using SQLite. Additionally, local storage is not suitable for storing large amounts of data like document content.

What is the benefit of using SQLite for caching in the browser?

Using SQLite for caching in the browser allows for faster page loads and navigation between pages by reducing the need to make network requests to the server, as the data can be read from the local disk-based cache.

How does the speaker describe the traditional client-server database setup?

The speaker describes the traditional client-server database setup as having a server running application code that communicates with a separate database server, typically via a protocol, where each process is an operating system unit with its own memory.

What is the difference between SQLite and traditional databases like PostgreSQL or MySQL?

SQLite is different from traditional databases like PostgreSQL or MySQL in that it does not require a separate server and runs alongside application code in a single process. It is designed for local data storage and is limited to the data that can be stored on the user's machine.

Why is WebAssembly important for running SQLite in the browser?

WebAssembly is important for running SQLite in the browser because it allows the browser to run code compiled from languages like C, C++, or Java, which can then interface with the file system API to perform tasks like reading and writing data to disk.

What is a Web Worker and how does it relate to the discussion in the script?

A Web Worker is a JavaScript API that allows you to run code in a separate thread, which is beneficial for performing computationally intensive tasks without blocking the main thread. In the context of the script, Web Workers are used to run SQLite operations for caching, improving performance.

What is the race condition strategy mentioned in the script and how does it improve performance?

The race condition strategy mentioned in the script involves making two requests simultaneously: one to read from the local cache and another to fetch data from the server. The data from the first request to complete is used, which can improve performance by ensuring that the fastest data source is utilized.

How does the speaker address the issue of data corruption in the SQLite cache?

The speaker addresses the issue of data corruption by using a shared Web Worker to manage cache writes. This ensures that only one process writes to the SQLite cache at a time, preventing concurrent writes that could lead to data corruption.

What does the speaker suggest about the role of ACID compliance in preventing data corruption?

The speaker suggests that although SQLite is ACID compliant, which should prevent data corruption due to concurrent writes, the issue of data corruption was actually due to the browser's file system API and not SQLite itself, highlighting the importance of considering the entire system architecture.