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I am a seasoned Fullstack Software Developer based in Zagreb, Croatia, with 17 years of experience in startups and large companies delivering high-performance, scalable solutions. I enjoy solving complex problems and keeping up with the latest trends in web and mobile development. I thrive in collaborative environments and have extensive remote-work experience across CET, PST, and EST time zones. My strengths include React, React Native, PHP, Node.js, microservices, and cloud-oriented architectures, and I am always eager to learn and adapt to new technologies and challenges.…I am a seasoned Fullstack Software Developer based in Zagreb, Croatia, with 17 years of experience in startups and large companies delivering high-performance, scalable solutions. I enjoy solving complex problems and keeping up with the latest trends in web and mobile development. I thrive in collaborative environments and have extensive remote-work experience across CET, PST, and EST time zones. My strengths include React, React Native, PHP, Node.js, microservices, and cloud-oriented architectures, and I am always eager to learn and adapt to new technologies and challenges.

Tomislav Kostantinov

Full Stack Developer, Web Developer, Back-End Developer, +2

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I am a seasoned Fullstack Software Developer based in Zagreb, Croatia, with 17 years of experience in startups and large companies delivering high-performance, scalable solutions. I enjoy solving complex problems and keeping up with the latest trends in web and mobile development. I thrive in collaborative environments and have extensive remote-work experience across CET, PST, and EST time zones. My strengths include React, React Native, PHP, Node.js, microservices, and cloud-oriented architectures, and I am always eager to learn and adapt to new technologies and challenges.…I am a seasoned Fullstack Software Developer based in Zagreb, Croatia, with 17 years of experience in startups and large companies delivering high-performance, scalable solutions. I enjoy solving complex problems and keeping up with the latest trends in web and mobile development. I thrive in collaborative environments and have extensive remote-work experience across CET, PST, and EST time zones. My strengths include React, React Native, PHP, Node.js, microservices, and cloud-oriented architectures, and I am always eager to learn and adapt to new technologies and challenges.

Available to hire

I am a seasoned Fullstack Software Developer based in Zagreb, Croatia, with 17 years of experience in startups and large companies delivering high-performance, scalable solutions. I enjoy solving complex problems and keeping up with the latest trends in web and mobile development.

I thrive in collaborative environments and have extensive remote-work experience across CET, PST, and EST time zones. My strengths include React, React Native, PHP, Node.js, microservices, and cloud-oriented architectures, and I am always eager to learn and adapt to new technologies and challenges.

Skills

Experience Level

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Intermediate

Intermediate

Language

Croatian

Fluent

English

Fluent

German

Intermediate

Work Experience

Software Developer at Coltech (self-employed)

January 1, 2025 - Present

Freelance work for various clients (e.g., DeeperSignals, KeeperSolutions, SmartCargo). Technologies used include PHP, SQL, React, and React Native.

Software Developer at E.ON

January 1, 2023 - January 1, 2024

Remote B2B role in E.ON Deutschland's finance team; developed, bug-fixed, and upgraded the power.cloud billing system using Symfony/PHP.

Software Developer at MiniFinder

January 1, 2019 - January 1, 2023

Created microservice architecture for IoT devices; built universal React web/mobile application and React Native mobile app; delivered end-to-end solution.

Software Developer at StormX Inc (STORM/STMX token)

January 1, 2018 - January 1, 2019

Developed backend administration application from scratch (React Native/Web, GraphQL, Node.js, microservices); registered STORM token with MetaMask; built React Native mobile app.

Software Developer at Tau Online

January 1, 2016 - January 1, 2018

Designed and implemented architecture for MojPosao job portal (1M MAU); developed portal search engine (Front/Backend/Sphinx); wrote cron scripts for various jobs and caching; developed Poslovac mobile app (React Native).

Software Developer at Goodgame Studios

January 1, 2014 - January 1, 2016

Developed backend applications for sales support (invoices, revenue calculations); built web portal for game publishers; contributed to in-game logic backend using React.

Software Developer at Adriatic.hr

January 1, 2012 - January 1, 2014

Led a team and developed backend applications for Croatia’s largest booking platform; implemented search engine optimizations, cron jobs, and SMS gateways; upgraded a custom PHP framework; integrated multiple APIs via XML, RPC, SOAP to synchronize offers.

Software Developer at MIPS

January 1, 2008 - January 1, 2012

Created an internal bug-tracking system for the Croatian Postal Service (PHP, Javascript, INFORMIX, SOAP); built a package registration application (JAVA EE); developed company website.

Web Developer at DIMEDIA

January 1, 2007 - January 1, 2008

Created 20+ CMS websites for major Croatian companies; upgraded in-house PHP framework.

Software Developer (Freelance) at Coltech (self-employed)

January 1, 2025 - Present

Provided freelance software development services for multiple clients, delivering PHP, SQL, and front-end/mobile solutions using React and React Native. Collaborated with clients in USA, Ireland and Slovenia; performed bug fixes, feature development, and system improvements.

Software Developer at StormX Inc

January 1, 2018 - December 31, 2019

Developed the backend administration application from the ground up (React Native web, GraphQL, Node.js, microservices); integrated STORM token with MetaMask; developed React Native mobile application.