A Substack post argues that software performance extends beyond speed metrics like API response times. It’s fundamentally about efficiency, sustainability, and the craftsmanship of writing code. The author emphasizes that every line of code consumes CPU cycles, which cost time, energy, and money, making performance a responsibility rather than a luxury for tech companies and developers.

Small inefficiencies scale into massive energy drains across millions of daily requests. Saving just 10ms on a frequently called function saves significant global CPU time. This mindset shift is crucial because performant code often means clearer logic, fewer database calls, and leaner abstractions, ultimately leading to more maintainable codebases rather than complex, unreadable hacks.

Most developers build applications, not operating systems, but that doesn't absolve them of performance responsibility. The collective impact of millions of developers writing slightly more efficient code results in faster web experiences and lower carbon emissions from data centers. Tools like Rails with Hotwire demonstrate how to build dynamic frontends without heavy JavaScript frameworks.

Ultimately, writing efficient software is a mindset valuing users' time and infrastructure costs. Optimizing queries or refactoring loops contributes to a global movement toward leaner, sustainable computing. The author concludes that performance is care—empathy translated into code where every cycle matters.