Lammert Westerhoff
Full Stack Developer at Toptal
Puebla City, Puebla, Mexico
Summary
👤
Senior🎓
Top SchoolLammert Westerhoff is a pragmatic full-stack developer and engineering leader with 12 years of experience, currently leading cross-platform mobile development at Forbes and co-founding fintech startup Fifty Fifty Card as CTO. He specializes in Kotlin Multiplatform and AWS infrastructure, has delivered consumer-facing apps used by millions at NS, ING and Eneco, and frequently works as a freelance mobile developer through Toptal and Paoapps. A certified Scrum Master and former team lead, he blends hands-on engineering with product-minded leadership and an entrepreneurial streak dating back to founding Stylbar. He champions AI-assisted development and is actively exploring ML and agent integration to accelerate daily workflows. His open-source contributions show attention to quality and accessibility—ranging from test automation for prerender-node to improving VoiceOver support in an iOS calendar component—reflecting a focus on robustness and inclusive UX. Based in Puebla, Mexico, he combines large-enterprise delivery experience with startup agility.
12 years of coding experience
18 years of employment as a software developer
Bachelor, Informatics, Bachelor, Informatics at Hanze
English, Dutch
Github Skills (18)
accessibility10
objective-c10
javascript10
ios10
sinon10
testing10
mochajs10
swift10
calendars9
expressjs9
datetime9
dates9
nodejs9
uid8
interface-design8
Programming languages (15)
Github contributions (5)
ruslanskorb/RSDayFlow
Sep 2015 - Mar 2016
iOS 7+ Calendar (Date Picker) with Infinite Scrolling.
Role in this project:
Mobile Developer (iOS)
Mobile Developer (iOS)Contributions:6 commits, 5 PRs, 4 comments in 6 months
Contributions summary:Lammert focused on improving the accessibility and functionality of the iOS calendar date picker, RSDAyFlow. They modified the code to better support VoiceOver by adjusting accessibility elements and labels. Additionally, the user fixed date calculations, removed redundant code and added the capability to customize fonts for the days of the week. These changes show the user’s commitment to creating a more user-friendly and accessible date picker.
date-pickerdatepickercalendarscrollscrollview
prerender/prerender-node
Apr 2014 - Apr 2014
Express middleware for prerendering javascript-rendered pages on the fly for SEO
Role in this project:QA Engineer / Test Automation Engineer
QA Engineer / Test Automation EngineerContributions:8 commits in 1 day
Contributions summary:Lammert primarily focused on testing the `prerender-node` middleware. Their commits involve writing and modifying test cases, specifically within the `test/index.js` file. The changes include adding tests, reorganizing existing ones, and refactoring testing logic. The user's work ensures the correct functionality of the middleware and its various features.
prerenderprerenderingjavascriptexpresson-the-fly
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