Şahin – React Native, React, OpenAPI

Client & Stakeholders: An algorithmic trading and research platform. The dashboard is used internally by the company's strategy developers and trading operators. Business Problem: The team ran day-to-day work through command-line tools, raw CloudWatch logs and an outdated dashboard spread across disconnected pages, which made it slow to compare strategies, follow backtests or react to live trading issues. Product: A single internal operations dashboard covering the full strategy lifecycle: a strategy catalog with side-by-side comparison, data charts, backtest runs and releases, plus live operations views for running instances, trades, profit and loss, alerts and logs.

• Led the rebuild of the internal dashboard as a dedicated React 19 and TypeScript app, replacing command-line tools, CloudWatch log digging and a fragmented legacy dashboard with one place for strategy and trading operations;
• Built the strategy catalog and comparison, data charts, and the backtest run and release flows for strategy developers;
• Built the operations screens for instances, trades, profit and loss, and alerts, with live log streaming inside the app;
• Set up a small design system with light and dark themes and a shared component library;
• Generated API types from the backend's OpenAPI spec, so breaking backend changes failed CI instead of reaching users;
• Added MSW API mocks and Playwright end-to-end tests, working with another developer on part of the scope.

A detective game with a React Native mobile app, a Node.js backend and a web part, currently in development and not yet released.

• Building the full product solo across mobile, backend and web;
• Designed a multi-session Claude Code workflow in which a coordinator session plans the work and delegates tasks to separate mobile and backend sessions;
• Keeps plans, the database schema and mobile–API contracts in a shared docs repo that all sessions work from;
• Reviews every change before it lands: Codex runs a second-opinion review before each commit, then he checks the findings and approves what goes in.

Client & Stakeholders: A Moroccan accommodation and travel booking marketplace preparing for launch, serving travelers and property hosts in English, French and Arabic. Business Problem: Before launch, the platform needed a reliable booking and payment experience, AI-powered help for travelers and hosts, and a fast, fully localized web app, including right-to-left Arabic. Product: A booking marketplace with instant booking and partial payments via Stripe, real-time host–guest messaging, interactive maps, an AI travel assistant, and an AI tool that writes listing descriptions for hosts.

• Cut home page first paint from 4.9s to 1.7s and shrank one bundle from about 8 MB to 44 KB (local tests) during the pre-launch performance work;
• Built the Stripe booking flow with instant booking, partial payments and automatic retries for failed card payments;
• Built the web side of the AI travel assistant, with streamed answers, chat history and source cards;
• Built an AI tool that writes listing descriptions for hosts;
• Fixed right-to-left layout issues across the English, French and Arabic versions and a socket reconnect problem in real-time messaging;
• Traced the cause of slow first video playback and handed it to the backend team, who shipped the fix.

Client & Stakeholders: A Swiss marina booking platform for boat owners and marinas, with 10K+ downloads on Google Play and 4,200+ marinas on its map. Business Problem: The app was several years old and well behind on React Native and library upgrades, which slowed down new feature work and left it relying on deprecated dependencies. Product: A mobile app and web platform where boat owners find and book guest moorings on a map, check in and pay at the marina, and share their own berth while they're away. Available in 10+ languages.

• Upgraded a years-old production app from React Native 0.61 to 0.72, React to 18 and React Navigation to 6, bringing the 10K+ download app back onto supported versions;
• Migrated state management from Redux to MobX and replaced deprecated libraries;
• Built the check-in-and-pay mode on the map and booking screens;
• Built the points of interest request screen and boat document upload with the camera;
• Built, on his own, the first version of a web tool for managing the app's and website's translations across 10+ languages.

Client & Stakeholders: A booking platform for shared offices, meeting rooms and virtual office packages, serving two audiences: customers booking space and the workspace operators running it. (No longer live.) Business Problem: Customers and operators needed a mobile-first way to book, enter and pay for workspace, and to manage offices, requests and payments, without going through the web app. Product: Two connected mobile apps: a customer app for booking, QR entry and QR payment, and an operator app for managing offices, roles, booking requests and payments.

• Started both React Native apps from scratch, a customer app and an operator app, and was the main mobile developer, working with one colleague;
• Built booking with real-time availability, QR entry and QR payment, push notifications, maps, and Apple, Google and LinkedIn sign-in;
• Built per-office roles, request approval and payment management in the operator app;
• Integrated the PayTR web checkout into the app;
• Published both apps to the App Store and Google Play and shipped updates.

A media app that grew from a VOD/IPTV player into a multi-platform product running on phones, Android TV, desktop and web from a single React Native codebase. It supports Chromecast, offline HLS downloads and a built-in web browser, and comes with a companion receiver app that connects over the local network.

• Worked as a core developer alongside the project lead, shipping one React Native codebase to iOS, Android, Android TV, desktop (Electron) and web;
• Built HLS and background downloads, and Chromecast support;
• Built Android TV support with remote control and TV cursor handling;
• Co-built the in-app browser, including its TV version;
• Built the companion receiver app's local network connection over TCP sockets and Zeroconf.

An Instagram analytics app with follower behavior analysis, hashtag suggestions using Google Cloud Vision, and in-app subscriptions on iOS and Android.

• Built ReportsX as an Instagram analytics app with follower behavior analysis.
• Implemented hashtag suggestions using Google Cloud Vision.
• Implemented in-app subscriptions on iOS and Android.
• Sole developer, including the Node.js API and server-side receipt validation.

A social media startup for car lovers.

• Built most of the backend with Node.js, Express, and MongoDB.
• Implemented real-time chat over Socket.io.
• Added push notification features.
• Contributed to the React Native app.

An online therapy platform for clients, counselors, clinics and admins. I worked full-stack. No longer live.

• Built Jitsi video sessions on the frontend and backend.
• Built PayU payments with refunds and commission, plus PayTR refund and result flows.
• Worked on the role-based screens, English and Turkish support, and the calendar.