Why performant code matters (but gets widely ignored), with Casey Muratori

August 26, 2026

AI Summary

5 min read

Performance engineer Casey Muratori, who has spent decades in game development and now runs the educational Substack Computer Enhanced, argues that most software runs 10 to 100 times slower than it needs to — and that this is not because optimization is hard, but because the industry has internalized the wrong approach to it. The conversation covers why performance is widely ignored, what "premature optimization" actually gets wrong, and what a working engineer can do to write faster code without becoming a low-level specialist.

Why Performance Gets Ignored (And Why That Is Changing)

Muratori identifies several structural reasons that explain why most developers and companies deprioritize performance. In enterprise software, the user is often not the purchaser; buying decisions are based on compliance, legal liability, and cost, not responsiveness. Monopoly effects also matter — a social network cannot be displaced on speed alone because network effects dominate. But Muratori also sees a genuine shift: over the past decade, sustained advocacy has started to turn the tide. He points to products like the Blick video editor and the Bun runtime, which explicitly pitch themselves on being dramatically faster than incumbents, and which have gained real traction. "It kind of does seem that pointing at this issue and saying this is something we should be doing better has not be

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What you'll learn

1 (00:02) **Why Performance Matters and Why It's Ignored** - Casey Muratori argues most software runs 10-100x slower than needed, and explains why the industry has deprioritized performance.
2 (15:54) **Three Reasons Performance Gets Ignored** - Casey breaks down why most developers and companies deprioritize performance.
3 (20:54) **The Napkin Math Trap** - Developers often lack a baseline for what hardware can theoretically achieve, leading to bad architectural decisions.
4 (26:05) **Why You Must Read Assembly (Not Write It)** - Casey argues assembly reading is an essential skill for serious performance work, and it's far simpler than most developers think.
5 (29:50) **"Premature Optimization is the Root of All Evil" Revisited** - Casey dismantles the common misuse of this phrase and explains when it's safe and when it's dangerous.
6 (36:18) **The Rewrite Trap** - Casey points out that if performance problems were really just hotspots, companies would never need to rewrite entire systems.
7 (42:16) **A Practical Learning Path for Performance** - Casey outlines what you actually need to learn to write performant code, and it's less than you think.

+ Full timestamped outline available in the app

Show Notes

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—

There can be few people around who care about software performance more than today’s pod guest, Casey Muratori. He’s a programmer and videogame developer, founder of Molly Rocket, and creator of Handmade Hero – a long-running series about building a game from scratch. He also evangelizes about performance on his Substack, Computer, Enhance.

We got to know each other about three years ago, first via messages, including this one from Casey:

“Why does the industry zeitgeist place so little emphasis on software performance when there seems to be overwhelming evidence that performance is critical to their bottom line?

Like you, I run a Substack for professional programmers, but I focus exclusively on software performance. Although we are quite large by Substack standards, so a certain subset of programmers must believe performance is important, I nonetheless hear lots of dismissive excuses when I post on social media. This happens so frequently, I devoted an entire article to cataloging the extensive pro-performance evidence we already have from the world's leading software companies: Performance Excuses Debunked.

Strangely, nobody has a rebuttal to why performance is important. When I point people to this, they actually tend to agree. But the prevailing attitude nonetheless stays the same.”

I’m delighted we finally have Casey on the podcast because it’s overdue! In this episode, we discuss why software performance matters, why it’s overlooked, and how developers can get better at writing performant code. We explore why performance should be considered during design, the value of learning to read assembly & understanding how CPUs work, Casey’s critique of ‘clean code’, and why he believes testing shouldn't drive software design.

We touch on how videogame development has changed, and influential game engines. Casey