Evrim is available for hire
Hire EvrimEvrim Persembe
Verified Expert in Engineering
JavaScript Developer
Istanbul, Turkey
Toptal member since October 5, 2020
Bio
Evrim is a software developer with a focus on web and mobile apps. He deeply cares about well-tested and maintainable code. Throughout his career, he has worked both in enterprise software and startups. He sees software development almost as an art form; he is also a realist that understands the business side of things. Evrim strives to get things done as quickly as possible without sacrificing quality.
Portfolio
Hoot App
React Native, Mapbox, Expo, User Interface (UI), React, Google Cloud, ESLint...
Next Breath, Inc.
Django, TypeScript, Python, React Redux, React Native, JavaScript, Expo, Redux...
Xometry
React Native, Objective-C, Swift, Expo, Terraform...
Experience
- JavaScript - 9 years
- APIs - 7 years
- TypeScript - 7 years
- React Native - 7 years
- React - 7 years
- Mobile Apps - 7 years
- Redux - 4 years
- Expo - 3 years
Work Experience
Lead Mobile Engineer
2025 - 2026
Hoot App
- Led a mobile development team (managing two developers) while architecting a scalable, production-ready React Native app (24k+ LOC) using the Rust-inspired Result<T, E> pattern for type-safe error handling.
- Engineered a battery-efficient geospatial system featuring real-time location heartbeats, point-in-polygon geofencing, and background location handling with graceful degradation.
- Built a high-performance, gesture-driven media viewer (Instagram Stories-style) using Reanimated worklets to run physics-based animations on the UI thread, maintaining 60 FPS on low-end devices.
- Designed a weighted content ranking algorithm for the user feed, utilizing a 7-factor scoring system (recency, proximity, engagement) to personalize content discovery dynamically.
- Collaborated with design to build a comprehensive Design System and component library documented in Storybook, ensuring UI consistency and reducing feature implementation time.
- Implemented a sophisticated "Optimistic UI" strategy using TanStack Query, enabling instant user feedback for complex interactions (voting/commenting) with automatic rollback capabilities on error.
- Established a complete DevOps and Observability pipeline, utilizing EAS Build/Update for OTA delivery and Sentry for deep performance profiling, crash tracking, and release monitoring.
- Architected a multi-provider Authentication system (Google, Apple, FB, X) with custom PKCE security, handling platform-specific constraints and back-end token exchange.
- Developed an intelligent media processing pipeline handling video capture, compression, and thumbnail generation on the device to optimize upload bandwidth and storage.
- Contributed to back-end services (NestJS/Node.js) and Open Source libraries, fixing critical bugs and implementing missing features to unblock mobile development velocity.
Technologies: React Native, Mapbox, Expo, User Interface (UI), React, Google Cloud, ESLint, Prettier, Storybook, Sentry, EAS, Turf.js, React Native Reanimated, React Native Unistyles, FontAwesome, OAuth, Facebook SDK, X (formerly Twitter) SDK, Google Sign-in, Firebase, Firebase Authentication, Zod, React Hook Form, React Query, TanStack Query, React Navigation, Expo Router, JavaScript, TypeScript, NestJS, PostgreSQL, Technical Leadership, Mobile App Design, App Store, Google Play Store, Mobile App Security
Lead Mobile Architect & Developer
2025 - 2025
Next Breath, Inc.
- Architected a production-ready React Native application using Expo SDK 53, React 19, and the new architecture, ensuring high performance and future-proof scalability.
- Engineered a modular, full-stack architecture with strict TypeScript typings and feature-based isolation (billing, onboarding, exercises) to maintain code quality across a complex codebase.
- Integrated robust monetization features via Stripe, handling end-to-end subscription lifecycles, payment method management, and gated content access.
- Established a sophisticated DevOps pipeline using Expo Application Services (EAS) with automated CI/CD workflows for development, preview, and production builds.
- Established a comprehensive design system and reusable component library documented in Storybook, utilizing centralized design tokens to streamline UI consistency and accelerate feature development.
- Optimized application stability and user experience through advanced Redux state management, offline persistence, and edge-to-edge UI implementation.
- Engineered a custom video playback engine for guided exercises using react-native-video, integrated seamlessly with a broader symptom tracking and analytics system.
Technologies: Django, TypeScript, Python, React Redux, React Native, JavaScript, Expo, Redux, Redux Toolkit, Redux Persist, Stripe, REST, React Native Reanimated, React Hook Form, Yup, React Navigation, Storybook, ESLint, Prettier, EAS, Technical Leadership, App Store, Google Play Store, Mobile App Security
Software Developer
2021 - 2024
Xometry
- Joined Fusiform Inc. and undertook their mobile app development responsibilities. Refactored and maintained their existing app while creating a new enterprise app from the ground up.
- Oversaw mobile app development following Fusiform's acquisition by Xometry and played a role in enhancing Xometry's web applications.
- Received commendations from team leaders and peers for the quality, readability, and documentation of my work.
Technologies: React Native, Objective-C, Swift, Expo, Terraform, AWS Command Line Interface (CLI), Amazon Web Services (AWS), AWS Lambda, Docker, TypeScript, Java, iOS, Android, Flask, Python, Jira, Figma, GraphQL, SDK Development, SDKs, Software Development Toolkits (SDK), Web API, CSS, HTML, APIs, Git, Microservices, Design Systems, Front-end, UI Components, Storybook, Responsive UI, API Development, OAuth 2, Mobile App Development, RESTFul APIs, Mobile Development, Full-stack Development, User Interface (UI), User Experience (UX), Architecture, Pixel Perfect, Native Mobile Apps, Expo.io, Software Architecture, Continuous Integration (CI), Web Development, REST APIs, Large-scale Projects, DevOps, REST, Mobile Apps, Technical Leadership, Hardware Integration, App Store, Google Play Store, Mobile App Security
Software Developer
2021 - 2021
Myca.ai
- Spearheaded mobile app development at Myca.ai, crafting a multi-platform app from scratch.
- Integrated the mobile app with the back end and launched on the App Store and Play Store.
- Facilitated the refactoring of Myca.ai's web app codebase, applying enhanced coding conventions and methodologies to boost efficiency.
Technologies: React, React Native, Redux, TypeScript, Web API, CSS, HTML, APIs, Git, Front-end, UI Components, Responsive UI, Mobile App Development, RESTFul APIs, Mobile Development, User Interface (UI), User Experience (UX), Architecture, Pixel Perfect, Animation, Software Architecture, Web Development, REST APIs, Mobile UX, REST, Mobile Apps, Technical Leadership, Mobile App Design, App Store, Google Play Store, Mobile App Security
Founder
2016 - 2019
Automated Hotel
- Developed a white-label tablet app solution for hotels, enabling them to gain insights into guest preferences, enhance upselling opportunities, and provide convenient access to hotel services.
- Handled business development, funding, and hiring for the startup.
- Hired and collaborated with a designer to create a top-class user experience for the app.
Technologies: Android, iOS, Swift, React Native, Hotels & Lodging, Hospitality, Ruby on Rails API, Ruby on Rails (RoR), GraphQL, SDK Development, SDKs, Software Development Toolkits (SDK), Web API, CSS, HTML, APIs, Git, Automated Testing, Design Systems, Front-end, UI Components, Storybook, Responsive UI, Mobile App Development, RESTFul APIs, Mobile Development, Full-stack Development, Firebase, User Interface (UI), User Experience (UX), Architecture, Pixel Perfect, Animation, Native Mobile Apps, Full-stack, Startups, Software Architecture, Continuous Integration (CI), Web Development, REST APIs, REST, Mobile Apps, Heroku, Technical Leadership, Hardware Integration, Mobile App Design, App Store, Google Play Store
Founder
2013 - 2015
Hotel Revenue Plus
- Founded a hotel consultancy with a partner in Dubai, UAE.
- Managed the company's online presence alongside business development and sales responsibilities.
- Offered technical assistance to hotels concerning their internal systems, such as OPERA Hotel Property Management Solutions (PMS), and websites.
Technologies: Hospitality, Hotels & Lodging, WordPress, Pixel Perfect, Mobile UX
Software Developer
2012 - 2013
Iba America
- Developed software that used a state-of-the-art time-series matching algorithm to find coil-matching mistakes, potentially saving plants huge losses.
- Utilized C# and .NET to handle the interoperability between the C# code and the algorithm written in C++.
- Designed a modern UI prototype that revolutionized their existing legacy design system.
- Finished and launched the project ahead of schedule.
Technologies: Enterprise, C#, .NET, Design Systems, User Interface (UI), User Experience (UX), Pixel Perfect, Software Architecture
Project History
Full-stack Real-time Vessel Tracking System
https://github.com/evrimfeyyaz/ais-viewerI designed and developed an end-to-end automatic identification system (AIS) viewer that tracks real-time maritime traffic.
• Built the back end in Node.js with Fastify to ingest streaming AIS data and store it in a spatially indexed PostgreSQL/PostGIS database.
• Developed REST APIs for querying vessels using a bounding box.
• Built the front-end web application using React and MapLibre GL JS, and the mobile application with React Native (Expo), integrating Mapbox maps to visualize live vessel positions across platforms.
• Built the back end in Node.js with Fastify to ingest streaming AIS data and store it in a spatially indexed PostgreSQL/PostGIS database.
• Developed REST APIs for querying vessels using a bounding box.
• Built the front-end web application using React and MapLibre GL JS, and the mobile application with React Native (Expo), integrating Mapbox maps to visualize live vessel positions across platforms.
Manufacturing Marketplace App for a Large Enterprise
https://www.xometry.com/workcenter/After FactoryFour (ex Fusiform) was bought by Xometry, I continued working with them. I was tasked with creating a mobile version of their manufacturing marketplace app.
I created the app from scratch using React Native, initially with a few small features. We used Expo for development, as I realized it was not mature enough. We also used EAS, and I handled the CI/CD system for automated test and production deployments of the app. On many occasions, my peers and superiors commended the quality and readability of my code.
I created the app from scratch using React Native, initially with a few small features. We used Expo for development, as I realized it was not mature enough. We also used EAS, and I handled the CI/CD system for automated test and production deployments of the app. On many occasions, my peers and superiors commended the quality and readability of my code.
Maintaining Xometry's Workcenter and Other Web Apps
https://www.xometry.com/workcenter/I started working for Xometry after they bought FactoryFour (ex-Fusiform). I was the sole mobile developer, handling three of their mobile apps. I was also tasked with helping them with Xometry Workcenter and their other web apps.
I mostly worked on React, but I occasionally also worked on back end, serverless (Python, Node.js, AWS Lambda), and DevOps (Docker, Terraform, AWS). Throughout my time there, I pushed for better documentation and software development methodologies. My peers and superiors commended me on many occasions for the quality and readability of my code.
I mostly worked on React, but I occasionally also worked on back end, serverless (Python, Node.js, AWS Lambda), and DevOps (Docker, Terraform, AWS). Throughout my time there, I pushed for better documentation and software development methodologies. My peers and superiors commended me on many occasions for the quality and readability of my code.
Mobile App for Streamlining Factory Work
https://learn.factoryfour.com/features/lightning-app/When I joined FactoryFour (ex-Fusiform, later bought by Xometry), they wanted to create a new mobile app that would streamline production tasks on the factory floor. I started working on it almost from scratch and created an app that was ready to be demoed in a short time. As a side note, I was really proud when the company owner demoed the app to their first potential customer, and it worked without any issues at all the first time.
This app used React Native and initially targeted Android tablets. It connected to a handheld QR code scanner through an SDK. I handled the maintenance and updates of the native module that consumed the SDK as well.
This app used React Native and initially targeted Android tablets. It connected to a handheld QR code scanner through an SDK. I handled the maintenance and updates of the native module that consumed the SDK as well.
O&P Manufacturing Management App
https://fusiform.co/cast.htmlFusiformCAST is a platform designed for orthotics and prosthetics (O&P) fabricators to automate manufacturing management. I handled the iPad app for this product, which was a product by FactoryFour (former Fusiform, later bought by Xometry).
I initially maintained the existing codebase, which was written in React Native, fixed bugs, and added new features. Later, I recommended refactoring the codebase to make it easier to work with. I refactored the codebase to use modern development methods and moved it from JavaScript to TypeScript.
The app used an external 3D scanner, and it communicated with the scanner SDK through a native module. I also handled the maintenance of that module.
I initially maintained the existing codebase, which was written in React Native, fixed bugs, and added new features. Later, I recommended refactoring the codebase to make it easier to work with. I refactored the codebase to use modern development methods and moved it from JavaScript to TypeScript.
The app used an external 3D scanner, and it communicated with the scanner SDK through a native module. I also handled the maintenance of that module.
AI-assisted Task Management App
https://www.myca.ai/I developed the initial version of Myca.ai's mobile app using React Native. As this was a new product from a startup, there were no designs, so I created the UI/UX for the app. I released the app in the app stores within a few weeks. I also helped Myca.ai with improving their existing React web codebase.
COVID-19 in Charts
http://covid19.evrim.ioA single-page web app that visualizes the COVID-19 data from Johns Hopkins University.
It contains various charts to understand the progression and the current status of COVID-19 at a selected location. It aims to be easy-to-understand at a quick glance.
It's been visited by thousands of people, and many people use it as a tool to update themselves on the status of the pandemic daily.
It contains various charts to understand the progression and the current status of COVID-19 at a selected location. It aims to be easy-to-understand at a quick glance.
It's been visited by thousands of people, and many people use it as a tool to update themselves on the status of the pandemic daily.
COVID-19 API
A JavaScript library that provides a simple API to access the Johns Hopkins University's COVID-19 data.
It is well-tested and has detailed documentation, and it was developed using TypeScript. I extracted this from another project that I worked on called COVID-19 in Charts to help other people access the JHU COVID-19 data.
It is well-tested and has detailed documentation, and it was developed using TypeScript. I extracted this from another project that I worked on called COVID-19 in Charts to help other people access the JHU COVID-19 data.
Song Practice Flashcards Creator | AI-powered Language Learning Tool for Song Lyrics
https://github.com/evrimfeyyaz/song-practice-flashcards-creatorI built a web application that helps users practice and internalize song lyrics through AI-powered analysis and flashcard generation.
I developed the entire system, which analyzes lyrics using GPT-4o to extract translations, IPA phonetics, and contextual meanings. I integrated AWS Polly to generate text-to-speech audio for pronunciation practice. The app generates customizable Anki flashcard decks for translation, pronunciation, and lyric recall, enabling effective and structured song-based language learning.
I developed the entire system, which analyzes lyrics using GPT-4o to extract translations, IPA phonetics, and contextual meanings. I integrated AWS Polly to generate text-to-speech audio for pronunciation practice. The app generates customizable Anki flashcard decks for translation, pronunciation, and lyric recall, enabling effective and structured song-based language learning.
Indie Sumo
A website that provides a list of resources for indie developers, bootstrappers, and solo entrepreneurs that I developed in my free time. You can view the source code at https://github.com/evrimfeyyaz/indie-sumo.
Education
2008 - 2011
Progress Toward a Bachelor of Science Degree in Mathematics and Computer Science
Ege University - Izmir, Turkey
Skills
Libraries/APIs
React, REST APIs, Web API, Ruby on Rails API, Node.js, React Redux, API Development, Redux Persist, Stripe, React Hook Form, Yup, React Navigation, Turf.js, Facebook SDK, X (formerly Twitter) SDK, Zod, React Query
Tools
Expo, Jira, Figma, Git, Expo.io, Firebase Authentication, JSX, Terraform, AWS Command Line Interface (CLI), Amazon Polly, Anki, Redux Toolkit, Prettier, Sentry
Languages
TypeScript, JavaScript, CSS, HTML, HTML5, SCSS, Ruby, Swift, Sass, Objective-C, GraphQL, C#, C, Haskell, C++, Java, Python
Frameworks
React Native, Ruby on Rails (RoR), Bootstrap, Redux, Jest, OAuth 2, Fastify, .NET, Flask, Django, NestJS
Paradigms
Object-oriented Programming (OOP), Testing, Mobile Development, REST, Test-driven Development (TDD), RESTful Development, Automated Testing, Microservices, Continuous Integration (CI), DevOps, Mobile App Design
Platforms
Mobile, iOS, Android, Amazon Web Services (AWS), AWS Lambda, Docker, Firebase, Mapbox, Heroku, WordPress
Storage
PostgreSQL, PostGIS, Google Cloud
Other
APIs, Enterprise, Mobile Apps, Mobile App Development, Architecture, Software Design, SDK Development, SDKs, Software Development Toolkits (SDK), Design Systems, Front-end, UI Components, RESTFul APIs, Pixel Perfect, EAS, Full-stack, Software Architecture, Web Development, Large-scale Projects, Technical Leadership, Hardware Integration, App Store, Google Play Store, Mobile App Security, Open Source, Hotels & Lodging, Hospitality, Mathematics, Algorithms, User Interface (UI), User Experience (UX), Push Notifications, Leadership, Storybook, Responsive UI, Full-stack Development, Native Mobile Apps, Design, Startups, Mobile UX, Vite, OpenAI GPT-4 API, OpenAI, Text-to-Speech (TTS), Supabase, Large Language Models (LLMs), Animation, React Native Reanimated, ESLint, React Native Unistyles, FontAwesome, OAuth, Google Sign-in, TanStack Query, Expo Router
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