João Fernandes
Co-Founder at SlashID
Lisbon Metropolitan Area Portugal
Summary
👤
Senior🎓
Top SchoolJoão Fernandes is a Principal Engineer with 14 years of experience building identity, security, and large-scale web platforms from early-stage teams to enterprise products. Currently at SlashID, he is shaping next-generation Identity-as-a-Service and Identity Protection capabilities while balancing hands-on engineering and architectural leadership. He has a track record of bootstrapping and scaling engineering orgs—hiring Lisbon’s first Salsify team and leading cross-functional groups at Onfido, RingCentral Events, and others. An active mentor with 50+ Plato sessions, he pairs senior coaching with practical delivery, helping engineers and leaders grow. His open-source contributions include extending the popular Ruby recaptcha library to support Google’s enterprise API, reflecting a habit of improving real-world developer tooling. Trained as a computer scientist (MSc/BSc, Instituto Superior Técnico), he blends rigorous research experience in real-time and concurrency systems with product-focused execution.
14 years of coding experience
12 years of employment as a software developer
MSc Computer Science, MSc Computer Science at Instituto Superior Técnico
Portuguese, English, Slovak
Github Skills (9)
testing10
ruby10
google-recaptcha10
api10
apidoc10
recaptcha10
rails9
configuration-management9
ruby-rails9
Programming languages (10)
Github contributions (5)
ambethia/recaptcha
Apr 2021 - May 2021
ReCaptcha helpers for ruby apps
Role in this project:
Back-end Developer
Back-end DeveloperContributions:3 reviews, 22 commits, 1 PR in 23 days
Contributions summary:João primarily focused on adding support for Google reCAPTCHA's enterprise API to the `recaptcha` Ruby library. Their contributions involved modifying the library's core logic to handle enterprise API calls, including changes to configuration, verification, and helper methods. Additionally, the user updated tests to reflect the new enterprise functionality and made minor code style improvements. This work extended the library's capabilities to support the enterprise version of reCAPTCHA.
recaptcharubyrailscaptchasinatra
bckground/starlark-go
Apr 2025 - Jun 2026
Starlark in Go: the Starlark configuration language, implemented in Go. :star:
Contributions:6 PRs, 51 pushes, 10 branches in 1 year 3 months
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