Yvo Cilon

Work Experience

Co-founder — Countoo

2025 – Present

Swift SwiftUI Core Data Watch Connectivity HealthKit watchOS

Co-founded and architected native iOS + watchOS app from concept to App Store submission
Designed flexible game engine supporting multiple sports (padel, tennis, football, basketball) with real-time score sync between iPhone and Apple Watch
Integrated HealthKit to automatically log workouts and calories burned during matches
Developed custom Watch complications enabling instant score access directly from watch face

React Native Developer (Freelance) — DPG Media

2025 – Present

React Native Expo TypeScript React Query Swift Kotlin AWS SST Sentry

Built consumer sports news app from scratch for major Dutch media company, surpassing legacy app with additional features
Integrated native advertising and analytics SDKs, enabling monetization and user behavior insights
Developed native modules (Swift/Kotlin) for platform-specific functionality not available in React Native
Architected serverless backend (AWS/SST) aggregating multiple data sources into a unified, performant API
Implemented push notification system with deep linking, driving user re-engagement
Optimized app performance and UX, reducing load times and improving user experience

Senior Front-End Developer (Freelance) — Schiphol

2025 – 2025

Remix TypeScript Contentful Storybook TailwindCSS New Relic Auth0

Delivered design system components for major airport rebrand, ensuring visual consistency across the platform
Built comprehensive Storybook documentation, improving developer experience and component discoverability
Developed CMS-driven components with Contentful, enabling content team autonomy
Resolved critical bugs in flight search feature, improving stability for millions of annual visitors
Enhanced accessibility (WCAG compliance): screen reader support, keyboard navigation, ensuring inclusive user experience
Improved Premium Services and Privium registration flows, streamlining customer onboarding

Senior Full-Stack Developer (Freelance) — Coinmerce

2023 – 2025

Next.js React TypeScript Flutter PHP DatoCMS WebSocket Mollie Pay.nl

Led complete Next.js V2 platform rebuild, migrating from Pages Router to App Router with SSR for improved SEO and performance
Built real-time trading interface with WebSocket-powered order book, live charts, and sub-second updates
Scaled PHP platform during rapid user growth, delivering new onboarding flows to handle increased demand
Implemented Flutter mobile features for EU MiCAR regulatory compliance, ensuring market access
Integrated Pay.nl payment gateway, expanding payment options for users
Established CI/CD pipelines, accelerating deployment cycles and reducing release friction

Full-Stack Developer (Freelance) — Techno Desk B.V.

2014 – Present

Node.js Remix PostgreSQL MySQL RabbitMQ Docker FFmpeg Electron Python Pygame C# WinForms WebSocket Mux

10+ year trusted partnership delivering diverse technical solutions across web, desktop, IoT, and video
Architected funeral management system: automated video processing (FFmpeg), queue management (RabbitMQ), real-time multi-location synchronization
Built Electron desktop media player with real-time backend sync, deployed across multiple client locations
Developed livestream platform (Mux) enabling remote attendance for funeral services
Created WinForms invoicing application - still in daily production use since 2014, demonstrating long-term reliability
Built interactive museum installations: Electron touch interfaces controlling Raspberry Pi projector networks
Developed hardware control systems: AMX controllers, serial protocols (RS-232/485), lighting and recording automation
Built municipal council chamber systems from scratch: Python/Pygame displays, camera switching, DCN microphone integration

Co-founder — Sidelyne

2021 – 2024

React Native Mapbox GraphQL Node.js PostgreSQL PostGIS React Vite

Co-founded sports discovery platform, building full product from concept to launched app with active users
Built React Native app with Mapbox: performant pin clustering, custom markers, real-time viewport-based queries
Architected GraphQL/Node.js backend with PostGIS geospatial engine: proximity search, bounding box queries, geofencing
Built React admin dashboard for content and partner management
Secured Decathlon partnership, implementing sponsored pins feature for retail store locations
Gained valuable startup experience in product development, user acquisition, and knowing when to pivot

Senior Mobile Developer (Freelance) — Kramp Hub

2021 – 2022

React Native GraphQL Node.js

Developed features for React Native e-commerce app serving agricultural sector
Refactored barcode scanner module, significantly improving scan reliability and user experience
Reduced production errors by fixing critical bugs, improving app stability tracked via Sentry
Architected GraphQL BFF layer: unified multiple backend APIs, optimized data for mobile consumption, implemented caching

Senior Full-Stack Developer (Freelance) — LeasePlan

2018 – 2021

React Redux Redux Saga TypeScript Solidity Node.js React Native GitLab Jenkins Datadog Auth0

Built 'My LeasePlan' customer portal: user dashboard, MOT planning, fines management with complex Redux Saga state orchestration
Pioneered blockchain innovation: developed NFT smart contracts (Solidity) for service center appointment scheduling
Early adopter of React Hooks (beta), building Web3 frontend for blockchain integration
Shipped React Native mobile features: service booking, vehicle management, Shell SmartPay location-based payments
Established CI/CD infrastructure with GitLab and Jenkins, streamlining team deployments
Integrated Datadog monitoring and Auth0 authentication, improving observability and security

Frontend Developer (Freelance) — &Niped

2017 – 2018

React TypeScript

Sole frontend developer: architected and delivered complete V2 platform rebuild from scratch
Built employee health monitoring platform serving both B2B (corporate clients) and B2C (individual users)
Developed complex questionnaire engine integrating physical test results for health assessments
Implemented healthcare-grade security compliance (Dutch healthcare regulations, comparable to HIPAA)
Owned entire frontend delivery end-to-end: architecture decisions, implementation, and deployment

Full-Stack Developer (Freelance) — TranspariX

2014 – 2018

C# Vue.js Classic ASP jQuery Python SQL

Built TMS V7 platform serving enterprise clients including ASML and PostNL
Developed real-time shipment tracking and unified API gateway for multi-carrier integration
Implemented enterprise integrations: SAP connectivity and SSO authentication
Automated development workflows, improving team productivity and reducing manual processes

Profile

Key Skills