Software is slow because of bad design, not slow languages
rseroter · x · 2026-10-24
Sean Goedecke pushes back on the claim that AI will make software faster by rewriting it in faster languages: most programs can't be meaningfully sped up by a rewrite in C or Rust.
The argument:
- Most real programs are I/O-bound: in a CRUD site, 50% of a request's time is database queries, so a rewrite can at best double speed (realistically 1.5x). Curl could be 100x faster in code and you wouldn't notice — it's all waiting on the network
- Slow languages already delegate hot paths to C-backed libraries, erasing much of the theoretical gap
- Conclusion: performance is a design problem — reduce I/O, add caching, parallelize — not a language choice; the AI-rewrite-for-speed thesis generally doesn't hold
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