Remote Ruby Kevin Newton on Ruby & Python, Prism, Psych-Pure, and Exreg
Feb 6, 2026
Kevin Newton, a language tooling engineer who built Prism, a pure-Ruby YAML parser, and a regex engine, talks about Ruby vs Python runtime trade-offs. He covers Prism’s goals and adoption, FreeThreadedPython and the GIL, error-tolerant parsing for IDEs, and building pure-Ruby parsers and regex VMs. The conversation mixes technical trade-offs with practical design stories.
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From Shopify To Meta Runtime Work
- Kevin Newton left Shopify, joined Meta, and found runtime work on Python similar to his Ruby experience.
- He values learning language runtimes and enjoyed his time on YJIT at Shopify.
Runtime Choices Shape Code And Culture
- Runtime design choices (GC, error handling) shape an ecosystem's code structure and culture.
- Ruby's mark-and-sweep and Python's refcounting produce pervasive, different engineering patterns.
Try Free-Threaded Python Carefully
- Consider alternate build targets like FreeThreadedPython to remove GIL constraints when needed.
- Expect compilation options and extra locking responsibilities when using free-threaded builds.
