Guillaume Gelin
Founding Engineer at Self-employed
Paris, Ile-de-France
Summary
🤩
Rockstar🎓
Top SchoolGuillaume Gelin is a founding engineer and seasoned software leader based in Paris with 14 years of experience scaling systems and teams from individual contributor to CTO. He builds high-impact platform and backend systems—having deployed multi-tenant Kubernetes clusters, real-time bidding APIs, and a customer data platform—while also founding and growing startups, raising €600k and driving product-market fit at Refty. A pragmatic minimalist and entrepreneur, he combines hands-on engineering (Python-focused open-source contributions to projects like the Qtile window manager and OpenAPI Python client) with strong hiring and organizational instincts proven at Numberly. Guillaume's work balances developer experience, business KPIs, and operational rigor, and he has a habit of trimming long feedback loops into rapid, data-driven iterations. At Formal and as a freelance consultant he now helps security-conscious teams control and understand their data across datastores and APIs.
14 years of coding experience
7 years of employment as a software developer
Epitech
French, English, Spanish
Stackoverflow
2,100reputation
71kreached
8answers
1question
pytest
top-5%
python
top-5%
Github Skills (40)
apim10
api-rest10
notion-api10
page-layout10
layout10
qt10
python10
api-design10
restful-api10
async10
configuration-management10
generator10
xwindow10
api10
httpx10
Programming languages (20)
Github contributions (5)
ramnes/notion-sdk-py
May 2021 - Jan 2023
The official Notion API client library, but rewritten in Python! (sync + async)
Role in this project:
Back-end Developer
Back-end DeveloperContributions:14 releases, 74 reviews, 115 commits in 1 year 8 months
Contributions summary:Guillaume primarily focused on developing and improving the Python-based Notion API client library. Their contributions included fixing project URLs, code formatting, and adjusting dependencies. They implemented core features such as `Client.search()`, `Client.databases.list()`, `Client.pages.retrieve()`, `Client.pages.create()`, and `Client.pages.update()`. Furthermore, the user added functionalities for handling body content, query parameters, and implemented `AsyncClient` with corresponding methods.
api-clientapinotionhttpxpython
qtile/qtile-examples
Apr 2014 - Jan 2021
Example configurations and scripts for Qtile
Role in this project:Full-stack Developer
Full-stack DeveloperContributions:13 commits, 7 PRs, 12 pushes in 6 years 10 months
Contributions summary:Guillaume primarily contributed to configuring and improving a Qtile window manager setup. Their work involved creating and updating configuration files, including keybindings, layouts, and widgets. The commits demonstrate the user's focus on customizing the user interface and functionality of the Qtile environment, with a focus on Python. They also refactored the configurations to enhance modularity and user experience, introducing features for customization.
configurationsqt5qtile
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