Kelvin Williams

Currently working as a full-stack mobile (iOS and React Native) and backend developer.

Available for freelance opportunities.

Enthusiastic about mobile development and particularly excited about React Native, which is why I started to showcase apps made with React Native and interview developers and team about their React Native experience.

I write about things I have learned and software development in general on my personal blog at

Contact me via [email protected] or via the Contact form below


Freelance Mobile Developer

Active Giving

  • Greenfield project in which I acted as the app architect and senior developer overseeing the technical aspects of the project and assisting the other developer on the project when needed.
  • Implemented key features and components such as GPS tracking, API calls and state management.
  • Set up distribution in both app stores.
  • December 2019 - Current

    Freelance Mobile Developer


  • Took over existing Rohpost app from previous developer and fixed various UI, UX and performance issues.
  • Implemented and fixed key features such as profile deletion (along with all associated data in firebase), a caching strategy to decrease firebase bandwidth usage and improve perceived app performance, and an improved, more security-conscious friend invite process.
  • Introduced TypeScript and cleaned up large parts of the code base.
  • Acted as a one-man mobile app development team.
  • Supported project until a successful relaunch in the app stores.
  • September 2019 - Current

    Freelance Mobile Developer


  • Took over kollex app from agency to continue development of key features, such as filtering products and analytics tracking.
  • Acted as a one-man mobile app development team responsible for implementing new features, fixing bugs store releases
  • Debugged and fixed performance issues impacting creation of shopping lists and ordering in collaboration with the product and backend team.
  • Successfully on-boarded new developer and did handover and knowledge transfer of the code base before leaving.
  • July 2019 - January 2020

    Freelance Mobile Developer


  • Started greenfield development of cross-platform Lykon Health Coach 360 mobile app from scratch in close collaboration with designers and product development team in a mobile team of two as mobile lead.
  • Responsible for implementing and delivering supplied user interfaces and functionalities.
  • Designed app and project architecture for efficient and scalable development.
  • Implemented key features regarding tracking habits to improve blood biomarkers.
  • Involved in refining proposed features with regards to feasibility and quick turnaround time
  • Published app in App Store and Google Play Store.
  • Delivered documentation and for knowledge transfer to remaining developers.
  • September 2018 - January 2019

    Full Stack Mobile (iOS, React Native) Developer

    Softgarden e-Recruiting

  • Took over the C​offi iOS​ app from previous team and successfully completed and published the app.
  • Created and published the softgarden iOS app in team of 3. Temporarily acted as team lead, responsible for provisioning and distribution of builds.
  • Ported the softgarden app to Android with React Native, and continuing development as a cross-platform app with one code base.
  • June 2016 - August 2018

    Freelance Mobile Developer


  • Took over Rohpost app from previous developer.
  • Finished the project by fixing bugs, implementing missing features and improving loading performance until the app was ready to be published in the app stores.
  • August 2017 - November 2017

    Student Employee and Master's Thesis

    Fraunhofer Fokus

  • Implemented a fuzzy reasoning eninge, for processing real-time measurements from radio transceivers for delivering facts about the spectral environment to a spectrum manager for dynamic spectrum access, to enable low-interference and robust communication in dense wireless environments. View thesis.
  • September 2015 - April 2016

    Internship and Student Employee

    Fraunhofer HHI

  • Implemented an automated fiber to fiber alignment algorithm for passive waveguide structures in LabView.
  • Conducted fiber-optic power measurements on detector chips for high data rate communication.
  • August 2012 - February 2014


    Technical University of Berlin

    Master of Science
    Computer Engineering

  • Master's degree in Computer Engineering with a focus on Networking, at the TU Berlin.
  • Thesis entitled: 'Design and implementation of a minimal context reasoning engine for robust dynamic spectrum access wireless communication.
  • Implemented proof of concept fuzzy reasoning engine in C++, for assessing and allocating spectral bands.
  • August 2014 - April 2016

    Universidad Politécnica de Valencia

    Academic year abroad
    Erasmus/Leonardo Scholarship

  • Academic year abroad studying Electrical Engineering at the Universidad Politécnica de Valencia.
  • July 2011 - August 2012

    Technical University of Berlin

    Bachelor of Science
    Electrical Engineering

  • Bachelor's degree in Electrical Engineering with a focus on telecommunications engineering.
  • Thesis entitled: 'Automation of fiber-chip alignments for passive waveguide structures'
  • August 2008 - August 2013


    Programming Languages & Tools

    • React Native

    • JavaScript

    • Node.js

    • Swift

    • iOS

    • Java

    • C

    • C++

    • Python

    • HTML

    • CSS

    • Git

    • (No)SQL

    • Nginx

    • Docker

    • Firebase

    • MobX

    Experienced with

    • Developing native (iOS) and cross-platform mobile apps with React Native
    • Web and Backend Development
    • Working in cross-functional agile team with both the Kanban & Scrum methodologies


    • Native Proficiency: English, German
    • Conversational: Spanish, Portuguese


    Contact me if you:
    • need to hire a versatile freelance software developer.
    • have any questions and want to find out more about the services I provide.
    • just want to say 'hello'.