Bryan O'sullivan
Chief Technology Officer at Real World Haskell
San Francisco, California, United States
Summary
🤩
Rockstar🎓
Top SchoolBryan O'sullivan is a seasoned technology leader and Chief Technology Officer based in San Francisco with 26 years of experience building high-performance systems and developer platforms. He combines executive leadership at companies like Meta, Zoox, and Voxel with deep hands-on systems expertise, having directly contributed to core Haskell projects such as GHC, Cabal, bytestring, network, and aeson. Known for scaling developer productivity and infrastructure—he led Developer Infrastructure at Facebook and shipped large source-control and build/test systems—he also has a long history of authoring influential technical books, including Real World Haskell. His open-source contributions show a focus on correctness, performance, and interoperability (IPv6 support, overflow fixes, refactors that enable extensibility), reflecting a pragmatic engineering mindset. Bryan bridges academia and industry through teaching roles at Stanford and by pioneering community-driven publishing workflows that collected thousands of reader comments. He brings a rare mix of low-level language/runtime know-how, production systems leadership, and a talent for turning collaborative engineering culture into measurable outcomes.
26 years of coding experience
28 years of employment as a software developer
BA Computer Science, BA Computer Science at Trinity College Dublin
Stackoverflow
395reputation
8kreached
4answers
0questions
Github Skills (37)
json10
filehandle10
testing10
text-manipulation10
file-descriptor10
build-system10
data-structure10
socket10
ipv610
encoding10
ghc10
cabal10
data-structures10
network10
descriptor10
Programming languages (9)
Github contributions (5)
haskell/text
Jan 2009 - Aug 2017
Haskell library for space- and time-efficient operations over Unicode text.
Role in this project:
Back-end Developer
Back-end DeveloperContributions:1280 commits, 31 PRs, 63 pushes in 8 years 8 months
Contributions summary:Bryan contributed to the Haskell/Text library by implementing and improving the `mapAccumR` function, a core feature for accumulating transformations on text data. They also addressed error cases by tidying up error messages and making the code more robust. Further contributions included adding new functionality with the portable line splitter and adding unit tests to maintain high-quality code.
haskellunicodestring-manipulationutf8string
haskell/aeson
Jan 2011 - Oct 2016
A fast Haskell JSON library
Role in this project:Back-end Developer
Back-end DeveloperContributions:642 commits, 51 PRs, 143 pushes in 5 years 10 months
Contributions summary:Bryan primarily contributed to the development of a Haskell JSON library. They implemented JSON encoding support, including the creation of an 'encode' function and related helper functions. The user made significant changes to the type system to include new features like a fromJSON for Double and Int, and refactored existing code, all of which indicates a focus on core library functionality.
haskell
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