John Lees-miller
Cofounder And CTO at Overleaf (Writelatex Ltd)
England, United Kingdom
Summary
🤩
Rockstar🎓
Top SchoolJohn Lees-miller is a seasoned technology leader and cofounder/CTO of Overleaf, guiding a collaborative LaTeX platform used by millions while blending product vision with hands-on backend engineering. With 16+ years building distributed systems and safety-critical control software, he helped deliver the Heathrow Pod driverless taxi and led simulation and control tooling for Personal Rapid Transit. His toolkit spans Java, C++, Ruby and functional languages, and he contributes to prominent open-source projects such as CodeMirror and rubyzip—improving test coverage and security hardening. A PhD in Engineering Mathematics underpins his work in statistical data processing and robust system design, and he brings an unusual mix of academic rigor, startup scaling experience, and low-level systems craftsmanship to product-facing infrastructure.
16 years of coding experience
14 years of employment as a software developer
BSc Hons Computer Science, BSc Hons Computer Science at University of AlbertaDoctor of Philosophy (Ph.D.) Engineering Mathematics, Doctor of Philosophy (Ph.D.) Engineering Mathematics at University of Bristol
English, French
Stackoverflow
206reputation
1kreached
3answers
0questions
Github Skills (27)
git10
javascript10
back-end-development10
testing10
java10
security10
ruby10
javas10
pathname10
file-handling10
codemirror10
test-automation10
bump9
jtest9
junit9
Programming languages (17)
Github contributions (5)
rubyzip/rubyzip
Aug 2018 - Aug 2020
Official Rubyzip repository
Role in this project:
Back-end Developer & Security Engineer
Back-end Developer & Security EngineerContributions:7 releases, 86 commits, 58 PRs in 2 years
Contributions summary:John primarily focused on enhancing the security and robustness of the rubyzip library. They addressed potential path traversal vulnerabilities by disabling symlink creation and implementing checks to prevent unsafe entry names. Furthermore, the user contributed to the quality of the library by adding tests to improve the extraction and validation of file sizes within the zip archives. They also bumped the version of the gem on multiple occasions and added a test for opening a buffer using an IO stream.
rubyzipencryptionrubyaes-encryptionzip
overleaf/overleaf
Jan 2015 - Jul 2022
A web-based collaborative LaTeX editor
Role in this project:Back-end Developer
Back-end DeveloperContributions:14 reviews, 115 commits, 6 PRs in 7 years 7 months
Contributions summary:John primarily worked on the back-end aspects of the Overleaf project. Their commits demonstrate expertise in Java, specifically within the `git-bridge` service. Contributions include debugging and resolving NullPointerExceptions, refactoring, and implementing test cases related to file handling and push operations. They also upgraded dependencies, particularly Jetty, and refactored API endpoints.
latex
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