Summary: How Prime Video Optimized Updates for 8,000+ Devices

This article is a summary of the original case study by Alexandru Ene, which can be found here. It explores how Prime Video manages updates for a wide array of devices and the role of WebAssembly (Wasm) in improving performance and stability.

1. The Challenge of Updating on 8,000+ Device Types

• Prime Video serves millions of customers on a vast range of devices, including gaming consoles, TVs, set-top boxes, and more.

• Updates traditionally required separate native releases for each device, impacting updatability and performance.

2. The Introduction of WebAssembly (Wasm)

• Prime Video began using WebAssembly (Wasm) to address the trade-off between updates and performance.

• Wasm allows high-level language code to run efficiently on any device and is a part of the Bytecode Alliance ecosystem.

3. Two-Part Architecture for Efficient Updates

• The Prime Video app features a two-part architecture: a high-performance C++ engine on the device and an easily updatable component.

• The on-device C++ layer includes a JavaScript virtual machine and key components, while the downloadable code comprises various components that used to be in JavaScript.

4. Benefits of Using WebAssembly

• By incorporating Wasm for certain elements of the app, average frame times on mid-range TVs improved significantly.

• Wasm offers performance benefits without requiring application teams to know or care about the change.

5. The Transition to the New Architecture

• Transitioning to the new architecture involved updating on-device components to include the Wasm VM.

• Communication between JavaScript and Wasm components was carefully managed to ensure the preservation of behavior.

6. Results of the Transition

• The switch to Rust and Wasm improved frame rate stability, speed, and reduced memory consumption.

• Total memory consumption for the Wasm VM was significantly lower, saving precious device memory.

• The small size of the Wasm module and fast VM start time had no adverse effects on app start-up time.

• The use of Rust enabled safer code contributions and access to high-quality libraries.

Conclusion: Prime Video's adoption of WebAssembly has resulted in improved performance, stability, and reduced memory usage, making it a successful investment.

Please note that for the full case study, you can refer to the original article here.