Janko Marklein
Senior Software Engineer at Contentful
Berlin, Germany
Summary
🤩
Rockstar🎓
Top SchoolJanko Marklein is a Senior Software Engineer based in Berlin with seven years of hands-on experience building reliable back-end and full-stack systems, currently at Contentful. Largely self-taught in code after formal studies in philosophy and creative writing, he brings analytical rigor and strong communication to API and TypeScript-driven projects. At Contentful he has improved core libraries and migration tooling—adding TypeScript support, refining type definitions, and hardening API behavior—while also contributing tests and bundling improvements for node/browser builds. His background as a published writer and philosopher informs a precise, user-focused approach to developer tooling and metadata modeling. Colleagues rely on him for thoughtful problem-solving that bridges technical depth with clear documentation and design.
7 years of coding experience
8 years of employment as a software developer
Master of Arts - MA, Philosophy, 1,2, Master of Arts - MA, Philosophy, 1,2 at Freie Universität BerlinBachelor of Arts - BA, Creative Writing, 1,3, Bachelor of Arts - BA, Creative Writing, 1,3 at Leipzig UniversityFull Stack Web Development, Full Stack Web Development at SPICED AcademyThe Complete SQL Bootcamp, Data Processing and Data Processing Technology/Technician, The Complete SQL Bootcamp, Data Processing and Data Processing Technology/Technician at Udemy AlumniAbitur, 1,2, Abitur, 1,2 at Wilhelm-Raabe-Schule Hannover
Polish, Spanish, English, German, French
Github Skills (15)
contentful10
typescript10
javascript10
typescripts10
sdk10
jestjs10
typescript-types10
jtest10
jes10
webpacker9
webpack9
apidoc9
api9
data-modeling8
testing7
Programming languages (7)
Github contributions (5)
contentful/contentful-migration
Dec 2019 - Nov 2022
🚚 Migration tooling for contentful
Role in this project:
Back-end Developer & API Developer
Back-end Developer & API DeveloperContributions:16 reviews, 91 commits, 60 PRs in 2 years 11 months
Contributions summary:Janko contributed to the migration tooling for contentful by implementing and updating several features. They worked on type checks, stopping resending deleted fields, and filtering out metadata from payloads. Their work included modifications to index.d.ts, test/unit/lib/offline-api/request-batches.spec.ts, and src/lib/offline-api/index.ts files, indicating work on data models and API logic. They also worked on the implementation of tag features.
contentfulmigrationtooling
contentful/contentful.js
Dec 2019 - Mar 2022
JavaScript library for Contentful's Delivery API (node & browser)
Role in this project:Full-stack Developer
Full-stack DeveloperContributions:1 release, 38 reviews, 26 commits in 2 years 3 months
Contributions summary:Janko primarily contributed to enhancing the codebase by implementing TypeScript support, addressing bugs, and refining existing functionality. They improved the type definitions, added retry limit checks, and ensured metadata was correctly incorporated into the entities. The user also reintroduced the webpack bundler for building node and browser bundles and re-integrated the version number into the User-Agent header. Furthermore, they focused on the unit tests by modifying and creating new tests for the changes.
contentfulapijavascript-librarybrowserjavascript
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