# Don't stop early: Case-folding source code at memory speed

DevFeed: [Don't stop early: Case-folding source code at memory speed](<https://devfeed.tech/articles/don-t-stop-early-case-folding-source-code-at-memory-speed-19849.md>)

Original publisher: [Read original article](<https://github.blog/engineering/architecture-optimization/dont-stop-early-case-folding-source-code-at-memory-speed/>)

Author: Alexander Neubeck

Published: 2026-07-31T16:00:00Z

Content type: article

Language: en

Sources: [GitHub](<https://devfeed.tech/sources/github.md>)

Topics: [Optimization](<https://devfeed.tech/topics/optimization.md>), [Code](<https://devfeed.tech/topics/code.md>), [FIRST](<https://devfeed.tech/topics/first.md>), [Rust](<https://devfeed.tech/topics/rust.md>)

Tags: [architecture-optimization](<https://devfeed.tech/tags/architecture-optimization.md>), [case-folding](<https://devfeed.tech/tags/case-folding.md>), [code-search](<https://devfeed.tech/tags/code-search.md>), [engineering](<https://devfeed.tech/tags/engineering.md>), [github](<https://devfeed.tech/tags/github.md>), [open-source](<https://devfeed.tech/tags/open-source.md>), [optimization](<https://devfeed.tech/tags/optimization.md>), [rust](<https://devfeed.tech/tags/rust.md>), [source](<https://devfeed.tech/tags/source.md>), [speed](<https://devfeed.tech/tags/speed.md>)

## AI overview

GitHub explains how it optimized case folding for source-code search. A branch-free ASCII fast path and byte-space arithmetic allow the open-source Rust casefold crate to process code at more than 45 GiB/s on a single core.

## Source excerpt

How a branch-free loop and byte-space arithmetic let GitHub case-fold every byte of code search at >45 GiB/s on a single core. The post Don't stop early: Case-folding source code at memory speed appeared first on The GitHub Blog.