Dario Rexin
Senior Software Engineer - Swift Compiler at Apple
Cupertino, California, United States
Summary
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Top SchoolDario Rexin is a Senior Software Engineer with 15 years of experience, currently advancing the Swift compiler at Apple from Cupertino. He specializes in low-level language and runtime work—designing compact value witnesses, layout-based pre-specializations, and fast lock-free concurrency primitives—that shrink binaries and boost generic performance. Dario has deep distributed-systems roots from Mesosphere and Marathon, and has improved reliability and allocators in projects like Apache Mesos. An active open-source contributor, he has influenced flagship projects including swiftlang/swift, swift-corelibs-foundation, Elixir, and Akka, and presented at WWDC and the LLVM Developers’ Meeting. He also led practical transitions such as containerizing Swift Linux builds and enabling arm64 toolchains, showing a blend of research-quality compiler design and pragmatic infrastructure engineering. Notably, his work often targets subtle efficiency wins—memory-leak fixes, interpreted witness representations, and mailbox scheduling—that pay dividends at scale.
15 years of coding experience
8 years of employment as a software developer
B.Sc. Computer Science, B.Sc. Computer Science at HAW Hamburg
German, English
Stackoverflow
24,305reputation
1.2mreached
296answers
4questions
playframework
top-5%
filtering
top-5%
dictionary
top-5%
slf4j
top-5%
sbt
top-5%
akka
top-1%
Github Skills (57)
mesos10
c-language10
back-end-development10
cloud-computing10
apidoc10
elixir10
foundation10
testing10
compiler-development10
memory-management10
akka10
corefoundation10
scala10
type-system10
api10
Programming languages (12)
Github contributions (5)
d2iq-archive/marathon
Apr 2014 - May 2015
Deploy and manage containers (including Docker) on top of Apache Mesos at scale.
Role in this project:
Back-end Developer
Back-end DeveloperContributions:7 releases, 475 commits, 204 PRs in 1 year 1 month
Contributions summary:Dario primarily contributed to the backend logic of the Marathon platform, focusing on features related to application deployment and management. Their work included implementing enhancements to the endpoint API to display app ports, improving proxy response handling, and adding support for updating application instances. The user also made changes to JSON serialization, added support for group deployment, and refactored existing code.
dockermesosdcos-orchestration-guilddcos
swiftlang/swift-corelibs-foundation
Mar 2020 - Nov 2022
The Foundation Project, providing core utilities, internationalization, and OS independence
Role in this project:Backend Developer
Backend DeveloperContributions:7 reviews, 31 commits, 40 PRs in 2 years 9 months
Contributions summary:Dario primarily focused on bug fixes and improvements related to the Foundation framework. They addressed memory leaks in PropertyListSerialization, fixed an issue with relative links in CFTimeZoneCreateSystem, and ensured libdispatch initialization before CoreFoundation. Additionally, the user improved code by using arguments of the same type in _CFMultiplyBufferSizeWithoutOverflow, and made constants immortal.
tvostranslationinternationalizationfoundationindependence
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