Turbopack, now the default bundler for Next.js, uses incremental computation to speed up builds. Instead of rebuilding everything, it caches fine-grained results. This approach tackles the complexity of caching, which can add CPU and memory overhead, but is essential for large-scale web applications needing instant iteration.

The system's core is a fine-grained cache built on value cells (`Vc<…>`). These cells track dependencies automatically, similar to signals in SolidJS. When a source file changes, only the functions that read that cell are marked dirty and recomputed, avoiding unnecessary work across the entire build graph.

This architecture draws from over a decade of research, including Rust-Analyzer's Salsa and Parcel. By building on lessons from webpack's challenges, Turbopack aims for predictable performance at scale. The next step is proving this automatic dependency tracking delivers on its promise for real-world, massive Next.js projects.