Every screenshot in my dev.to posts has the same caption: "All tests run on an 8-year-old MacBook Air." That's not a disclaimer. It's a design constraint. The machine 2017 MacBook Air. 1.8GHz dual-core Intel Core i5. 8GB RAM. No discrete GPU. No Apple Silicon neural engine. The slowest Mac you could reasonably use in 2026. This is my primary development and testing machine. What it breaks immediately Anything that renders everything at once. Loading a 200-page PDF and rendering all pages to images: the app freezes. This is how I discovered I needed virtual scrolling. The problem was invisible on modern hardware — which means I would have shipped a broken experience to half my users if I'd developed on a fast machine. Synchronous operations on the main thread. On fast hardware, 200ms is invisible. On this machine, it's a visible stutter. Everything that takes more than a few milliseconds lives in a background thread — not as best practice, but because the 2017 Air demanded it. Memory-heavy caches.…