Recommended expert
Timm Preetz
Senior Backend-Framework Engineer
Experience
Jan 2025 - Jul 2025
7 monthsSenior Backend-Framework Engineer
Serverpod AB
- Improved the database migration engine to handle more edge cases
- Added support for Dart record and container types in the client-server protocol and PostgreSQL data storage
- Created the next generation authentication module: overhauling the social login; adding JWT, passkey, and magic link support; supporting legacy accounts in a backwards compatible way
Dec 2023 - Dec 2024
1 year 1 monthSenior Mobile App Developer, Energy supply contract sales & PV app
TELESON Vertriebs GmbH
- Built new Flutter mobile app version replacing two separate Android and iOS code bases (porting business logic from Swift and Kotlin)
- Added full offline support using local databases (Hive, Floor) and implemented a robust sync framework to update the server once the client regains network access
- Set up testing infrastructure and introduced CI workflows with CodeMagic
- Sped up client development by auto-generating APIs from the OpenAPI specification
- Implemented on-device PDF editing workflows for filling and signing forms
Jul 2023 - Sep 2023
3 monthsSenior Full-Stack Developer, Arabic language chat-bot app
Mawdoo3
- Built the MVP chat-bot app for the client’s custom Arabic GPT-style LLM using Flutter
- Wrote the backend for the app: user management, chat history, interfacing with the gRPC ML API services
- Communicated with downstream app and upstream Python-based AI backends via gRPC
- Set up CI/CD with deployments to Google Cloud Run from GitHub
Dec 2021 - Jul 2022
8 monthsSenior Full-Stack Developer, video conference & collaboration app
Buzz
- Extended the cross-platform Flutter app for video conferencing, work chat, and productivity on web, macOS, and an always-on toolbar app
- Replaced the single-server backend with a horizontally scalable Go backend that communicated via gRPC
- Used PostgreSQL, Redis (including PubSub), and S3 for data storage
- Introduced CI/CD with automatic deployment to AWS Fargate/ECS
Jul 2021 - Oct 2023
2 years 4 monthsSenior Mobile Developer, fitness studio management software and end-user booking app
MySports GmbH & Magicline GmbH
- Supported the release of three new end-user white-label mobile apps using Flutter
- Rewrote the white-label apps to share most code between them with OpenAPI
- Implemented a new UX and design system
- Taught the client’s existing team development best practices
- Introduced automated tests to the codebase and steadily increased coverage, ending with a CI/CD flow
- Led the development of the new Magicline app for studio personnel from scratch
May 2021 - Present
4 years 9 monthsSenior Full-Stack Developer
Toptal, LLC
Listed as a verified senior full-stack developer
Jul 2018 - Nov 2021
3 years 5 monthsDeveloper / Ops, farm workflow-support app
DataHarvest
- Brought the app to a release-ready state using Flutter
- Set up CI/CD for automatic tests on GitLab runners and releases with CodeMagic
- Fixed issues with native dependencies
May 2018 - Jul 2021
3 years 3 monthsFlutter Lead Developer – Mobile App
ABOUT YOU GmbH
- Completed rewrite of existing native Android and iOS apps in Flutter
- Deployed the company’s first backend microservices with Go and gRPC using Docker
May 2018 - Jul 2021
3 years 3 monthsHead of Architecture (Shop Applications)
ABOUT YOU GmbH
- Saw the new native app written in Flutter through to release as team lead
- Migrated code from legacy backends to new services
- Prototyped and kickstarted various new projects including backend systems and customizable shop applications for SaaS cloud customers
- Engaged in public speaking
May 2018 - Jul 2021
3 years 3 monthsSenior Frontend Developer & Team Lead – Mobile Web
ABOUT YOU GmbH
- Completely rewrote the existing mobile website in TypeScript, React, Redux, and Redux Saga
- Implemented PWA functionalities including service workers and offline capabilities
- Optimized performance and ensured responsiveness
- Introduced automated UI testing
May 2018 - Jul 2021
3 years 3 monthsTechnical Sales & Prototyping
ABOUT YOU GmbH
- Consulted on various smaller projects inside the company including technical sales and prototyping for the emerging SaaS/Cloud business SCAYLE
- Served as contact person for backend development and architectural questions
Oct 2017 - Apr 2018
7 monthsGame Developer, HTML5 Transpilation
Goodgame Studios & Altigi GmbH
- Ported Flash-based browser games to HTML5 by improving tooling to transpile AS3 to TypeScript
- Developed a Selenium-based testing setup to automate cross-browser tests
- Improved game performance by replacing slow parts in core libraries
Sep 2015 - Sep 2017
2 years 1 monthTeam Lead UI Components
XaaSify Technologies GmbH
- Led migration of a customer-facing realtime application from jQuery to React using a Flux architecture and event-based client-server communication
- Implemented a pull-request based workflow with CI oversight to maintain standards
- Created internal Node.js tools for dependency management, unit testing, visual diffs, and example runner/playground
- Designed a new component-based software development architecture for upcoming major projects
Sep 2012 - Feb 2016
3 years 6 monthsCo-Founder, Software Developer
Lunados UG (haftungsbeschränkt)
- Provided custom development and consulting to help e-commerce platforms increase reach and optimize offers using competitor analysis
- Built a fully automated system on Google App Engine and Azure to track hotel prices on competing platforms
- Developed GROWTH-Project to dynamically optimize landing pages and promote deals with SEA campaigns
- Created SEO-Logalizer in-house tool to analyze server log files
- Served as initial employee for an international bus search site, created technical proof of concept, built internal tools to manage bus companies and routes, connected over 100 external partners via inbound APIs and web scraping
Mar 2010 - Dec 2012
2 years 10 monthsSoftware Developer
ingsoft GmbH
- Ported the desktop application IngSoft InterWatt to a single-page web application using Backbone.js and a HTTP API
- Implemented bi-directional data synchronization between internal and on-premise Silverlight systems
- Created an Energy Savings Check app for a major Austrian energy company deployed to civilian customers in Silverlight
- Ported parts of the desktop app from Win32 to WPF to improve user experience
- Added ambitious features critical for the sales team to acquire large customers
Summary
Full-stack development, to me, spans the breadth from an initial idea to a production rollout and ongoing support. While my focus is primarily on the technical design and implementation, I am capable of handling each aspect of the entire process – though specialist contributions are always welcome.
Beyond the planning and programming of the actual software, I bring my expertise to the entire development workflow: how to test the product (continually and before each release), how to align deployments, how to monitor the entire running system and handle second-level support for users.
Recently, I have been mostly focused on delivering mobile applications, though I am happy to apply my experience to any part of the software stack that will benefit from my contributions.
Skills
- Flutter / Dart
- Go
- Grpc
- Openapi
- Postgresql
- Redis
- Aws
- Google Cloud
Languages
German
NativeEnglish
AdvancedFrench
ElementaryEducation
Oct 2009 - Jun 2010
Friedrich-Alexander-Universität zu Erlangen-Nürnberg
Business Informatics · Erlangen, Germany
Oct 2000 - Jun 2009
Engelbert-Kaempfer-Gymnasium
General Qualification For University Entrance · Lemgo, Germany
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