# SWC with DongYoon Kang

Page: https://stenobird.com/podcast/rustacean-station/swc-with-dongyoon-kang
Text version: https://stenobird.com/podcast/rustacean-station/swc-with-dongyoon-kang.md
Podcast: [Rustacean Station](https://stenobird.com/podcast/rustacean-station)
Published: 2025-05-31T07:01:00+00:00
Episode link: https://rustacean-station.org/episode/dongyoon-kang/
Audio file: https://dts.podtrac.com/redirect.mp3/audio.rustacean-station.org/file/rustacean-station/2025-05-31-dongyoon-kang.mp3
Processing state: processed
JSON: https://stenobird.com/v1/public/podcasts/rustacean-station/episodes/swc-with-dongyoon-kang
Duration seconds: 1490

## Resource

DongYoon Kang, the creator of SWC, explains how he built a high-performance Rust-based web compiler to solve the latency issues inherent in JavaScript-based tools like Babel. The discussion covers the technical transition from single-threaded JavaScript to parallelized Rust and the evolution of SWC into a core dependency for Next.js and Deno.

## Highlights
- Main idea: SWC was born from the need to eliminate the multi-second delays in web development caused by the single-threaded nature of JavaScript-based compilers
- Technical approach: The project leverages Rust's ability to perform heavy parallel processing, overcoming the fundamental event-loop limitations of Babel
- Practical takeaway: Building complex parsers can be achieved by studying existing implementations like Babel and porting core logic to Rust
- Failure mode: Expanding the compiler to support new languages like Dart is often limited by the maintenance burden of managing complex AST definitions
- Future direction: The development of a cross-module optimizer to automate sophisticated code optimizations within the compiler

## Topics

SWC, Rust, Web Development, Compiler Design, AST, Performance Optimization, JavaScript Tooling, Open Source Maintenance

## Chapters
- 1:00 — Using SWC AST for GraphQL: The host shares a personal experience using SWC's AST to automate the generation of TypeScript files from GraphQL schemas.
- 2:40 — The Motivation: Eliminating Latency: DongYoon Kang describes the frustration of waiting for HMR updates and the decision to build a faster alternative in Rust.
- 6:15 — The Rise of SWC and Deno: A look at the early years of SWC and how adoption by projects like Deno drove significant community contributions.
- 9:45 — Implementing Parsers and Lexers: Insights into the technical challenges of writing a high-performance parser by referencing the Babel source code.
- 11:40 — Optimization and Community Contribution: How the project manages performance profiling and coordinates a global, asynchronous team of contributors.
- 21:20 — The Challenges of Language Expansion: Why the creator decided against adding Dart support due to the high cost of maintaining new AST structures.
- 23:05 — Future Plans: Cross-Module Optimization: A glimpse into upcoming features, including a new module designed for smart, automated code optimizations.

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## Transcript

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