Robert Tessler - Full Stack & Mobile Developer

Robert Tessler - Full Stack / Mobile Developer

******.*******@*******.*** +31-061*-***-*** / Delft, NL https://linkedin.com/in/roberttessler https://github.com/rtessler SKILLS

Core Languages Python, Javascript, Typescript, Java, Kotlin, C++. Frontend React.js, Next.js, Vue.js, Three.js, Unity. Backend Node.js, FastAPI, Django, Spring Boot, .NET Core, GraphQL. Mobile Swift / SwiftUI, Jetpack Compose, React Native, Flutter. Database Postgres, MongoDB, MySQL, Redis, ORMs.

Cloud AWS (Lambda, S3, EC2, ECS), Firebase, Supabase. Dev Ops & CI/CD Github Actions, Gitlab pipelines, Docker, Kubernetes, Fastlane. AI & ML RAG, Langchain, OpenAI API, LLMs.

Other Technical Lead, System Architecture, Agile Methodologies. WORK EXPERIENCE

SixOfNine Engineering Delft, Netherlands

Software Consultant Jul 2025 …

• Engineered a Python/FastAPI mage processing service using ML for black-and-white to colour photo conversion. Deployment of containerized services using AWS Lambda, S3, IAM, EC2, ECS, Docker and Kubernetes.

• Developed a IOS / Android offline music player app using Swift / SwiftUI, Android Kotlin, Jetpack Compose, MVVM, React Native.

• Built a vocal replacement VST plugin, coding in C++11, DSP and JUCE framework.

• Developed an architectural 3D visualization web app and model generation using RAG, OpenAI API, Langchain, LLMs.

• Frontend development in React.js, Vue.js, Typescript, OpenGL, Three.js and Unity for interactive data visualisation.

Poolder Rijswijk, Netherlands

Full Stack Developer, Contract Jan 2025 - Jul 2025

• Architected and deployed a SaaS crypto currency trading platform using React.js, Next.js, TypeScript, Postgres, Tailwind and ApexCharts.

• Created secure admin interfaces for monitoring and processing orders and improving onboarding workflows.

• Enhanced data visualization components for tracking client asset values.

• Improved user experience by added buy and sell notifications, messaging functionality.

• Utilised Supabase for backend edge functions deployment to Vercel using Docker and Gitlab pipelines

Sping Delft, Netherlands

Mobile / Full Stack Developer, Permanent Sep 2023 - Sep 2024

• Development on QC One React Native / TypeScript inspection app used by 18,000 users. Optimised networked data sync, MobX State Management, Realm database, Sentry logging, notifications, fast rendering, unit and integration testing using Jest.

• Reduced download times for the Tessa Android / Kotlin app using GraphQL, Coroutines, Flow, Room DB, Retrofit, Hilt, MVVM, Jetpack Compose and Clean Architecture.

• Deployed to IOS and Android app stores using GitHub actions CI/CD and Fastlane.

• Conducted a research project on selective noise cancelling; Python, FastAPI, React.js.

• Created an energy usage calculator for the energy sector, algorithmic coding in Kotlin. Sway Music London, Remote

Mobile Developer / Tech Lead, Contract Feb 2022 – May 2023 Engineered a cross platform music streaming app for sharing playlists between Apple Music and Spotify. Coding in Flutter, Swift, SwiftUI and Kotlin.

• Developed an innovative cosine similarity text similarity song matching algorithm

• Developed a Flutter app, a SwiftUI app plus IOS and Kotlin native components for audio playback using Apple Music and Spotify APIs.

• Use of Google Vision API, GCP. Implemented notifications, chat functionality, audio streaming, real time update. Figma designs, app store deployment, OAuth2 authorisation, UI/UX design.

• Firebase backend development database operations and image upload. API development in Node.js / Express.js, Javascript, Python, Authentication, Cron based scheduling.

• Developed an admin portal in React.js for monitoring users and playlist generation. KNAB Amsterdam

IOS Developer, Contract Apr 2021 - Aug 2021

Improved the KNAB banking app onboarding flow to make signup simpler and increase client registration numbers. Use of IOS Swift, UIKit, Core Data, Reactive Programming, MVVM, OOP.

Sublime X Sydney, Remote

Mobile Developer, Technical Lead, Contract May 2019 - Apr 2021

• Developed a mobile Flutter app and admin web site in React.js / Redux for Marine Rescue NSW for reporting marine hazards in coastal waters. The MRNSW Risk App.

• Created an IOS Swift app and React.js web app for the Pepsi Cola Taste Challenge.

• Deployed to IOS and Android app stores

• API development in Firebase and GCP using Node.js, Express.js, Typescript and Python. Image upload, OAuth2 authentication, PDF generation.

• Did maintenance of the APTC Fiji technical college website using.NET Core, C#, ASP.NET, .NET MVC, HTML, CSS, SASS and Sitefinity CMS.

• Implemented automated data processing and data upload into a Hubspot CMS for Crescent Wealth using Python, Pandas, shell scripts, Java, Spring Boot, Maven, Redis, Kafka messaging and AWS.

Saatchi & Saatchi Sydney, Australia

Full Stack Developer, Contract Mar 2018 - Apr 2019

• Built a React.js hearing test web app for Cochlear with Marketo and Salesforce REST API integrations; unit and integration tested with Jest.

• Developed a Node.js/Express.js API on AWS (S3, Lambda, API Gateway) for Toyota kiosk JSON data uploads.

Deloitte Sydney, Australia

Front End Developer, Contract Feb 2017 - Jul 2017

Delivered the Australian Tax Office Relationship Access Manager in Angular, TypeScript, RxJS and Bootstrap with Jasmine.js testing in an Agile team. Landsberry and James Sydney, Australia

Full Stack Developer, Permanent Aug 2013 - Sep 2016 Built ad campaign analytics and an interactive page builder in JavaScript, Angular, jQuery; Java/Spring Boot, MySQL, AWS backend.

Publicis Groupe Sydney, Australia

Full Stack Developer, Permanent May 2011 - Jun 2013 Built and enhanced client-facing .NET/ASP sites (Audi, Unilever, Unity Water) using C#, ASP.NET MVC, SQL Server, JavaScript Backbone.js, jQuery. Devotion Digital Sydney, Australia

Full Stack Developer, Permanent Sep 2009 - Mar 2011 Development and maintenance of multiple ASP.NET sites. Coding in Kentico CMS and .NET C#. Updated the wool.au website using Java, J2EE, Spring and WebSphere. Deutsche Bank Sydney, Australia

Desktop App Developer, Permanent 2000-2005

Created a derivatives auto-trading desktop app in C++ used by traders globally for automated opportunity detection.

EDUCATION

Graduate Certificate Applied Science, Bioinformatics, Sydney University, 2003 Computer Science Honours, BSc, Sydney University, 1986 Bachelor of Science, BSc, Sydney University, 1983

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