Android App LOOKOO.de…

Project: Full-stack development of the native app and server backend. Custom geo-spatial search engine with privacy obfuscation, bespoke web services, classifieds, 400k+ events, coupons, anonymous chat, and persistent waiting sockets replacing HTTP polling.

Description: Full-stack architecture, end-to-end development, and five-year lifecycle maintenance of the native Android application "LOOKOO.de" alongside its comprehensive custom server backend as a high-traffic regional discovery and social platform. Designing and engineering a high-performance geo-spatial search engine for location-based networking, events, and coupon aggregation, incorporating privacy-preserving obfuscation algorithms for search results within a 2 km radius. Developing custom web services and backend APIs from scratch for seamless data orchestration and client communication. Building a scalable communication framework supporting anonymous chat IDs, global user discovery, and robust anti-spam protection against mass messaging. Core engineering focus centering on designing a low-latency, quasi-real-time messaging engine using persistent waiting sockets instead of traditional HTTP polling to guarantee minimal response times. Integrating self-developed server infrastructure for synchronizing over 400,000 regional events, classifieds, and location-based discount models, ensuring encrypted data transmission (SSL/TLS) to European server deployments.

Software: Android, Java, Kotlin, Interface specification, Sockets, Web-Objects, Web service, XML

Period: Jun. 2013 – 01.06.2018

PHOTUX-Track - Android shipping control…

Project: Development of a client-server app for print fulfillment workflows. Streamlined operations via barcode scanning, image processing, bundle grouping validation, automated shipping cost calculation, and dynamic PDF templating for labels and manifests.

Description: Architecture and end-to-end development of a native Android client-server application designed for automated control and quality assurance in fulfillment workflows for personalized print products (photo books, calendars). Engineered robust barcode-scanning pipelines featuring asynchronous image processing and instant cover-photo rendering for immediate visual verification post-scan. Implemented complex business logic for grouping and bundle validation (Zupackartikel): the system verified order completeness, automatically blocking label generation and triggering alerts if companion items were missing. For complete lots, integrated dynamic algorithms to calculate accurate shipping costs and optimal packaging sizes. Developed a high-performance PDF-templating engine to automate the generation of shipping labels, packing lists, and dispatch manifests containing cover thumbnails and postal routing codes for postal drop-off. Implemented an integrated image-capture pipeline to securely document packaged items prior to final dispatch. Connected to backend systems via HTTP protocols, XML interfaces, and web services for real-time order status tracking ("delivered") and dispatch notifications.

Software: Android, Http protocols, Java, PDF-Templating, Interface specification, bar code, Web service, XML

Period: 14.04.2015 – 26.05.2015

Android VoIP softphone app…

Client/end customer: technidoo UG, Swyx Solutions AG

Project: Development of a native VoIP softphone for SwyxWare. Custom SIP stack modifications, iOS-parity history management, server synchronization for contacts/favorites, and seamless integration of Android Bluetooth and car audio stacks for headsets.

Description: Architecture and end-to-end development of a native Android VoIP softphone client tailored for enterprise integration within the SwyxWare PBX environment. Designed and executed deep modifications to the SIP communication stack to accommodate proprietary Swyx protocol deviations, ensuring rock-solid registration, signaling, and call handling. Developed a sophisticated UI layer and engineered a complete overhaul of the history management subsystem to achieve strict iOS cross-platform parity. Implemented a robust audio routing architecture featuring tight integration with the Android Bluetooth stack (managing HFP/A2DP profiles for wireless headsets) and car audio systems, including proper audio focus handling and hardware button routing. Implemented high-performance local database modeling and server synchronization pipelines utilizing Retrofit, Jackson2, and RxJava for enterprise contacts, recent call logs, and favorites. Ensured mission-critical application stability and maintainability through advanced dependency injection (Dagger) and comprehensive automated test suites using JUnit, Mockito, and Espresso.

Software: Android, Ansi C, Butterknife, Dagger, Database modeling, Espresso, Glide, Http protocols, Jackson2, Java, Junit Tests, Mockito, ReactiveX/RxJava, Retrofit, SIP Protocol, XML

Project management: GIT, Gradle, Jenkins, Maven, Scrum

Period: 03.09.2015 – 02.12.2016

Further development of a house control app…

Client/end customer: Gira Giersiepen GmbH & Co. KG

Project: Enterprise evolution and legacy migration (GCM to FCM) of a KNX smart home app for heterogeneous hardware. Delivered WebRTC video streaming for IP intercoms, IoT sensor integration, server-driven UI, and a resilient offline-first architecture.

Description: Comprehensive enterprise-grade evolution, legacy migration, and architectural modularization of a mission-critical Java application designed for holistic KNX building automation and interfacing with the Gira HomeServer. Engineered and maintained a robust multi-flavour architecture enabling a unified codebase to power highly heterogeneous hardware targets—ranging from fixed in-wall wall tablets and the dedicated KNX room control device Gira G1 to mobile Android smartphones. Spearheaded the design and implementation of low-latency real-time media streaming modules for IP door intercom systems utilizing WebRTC, securely integrated across network segmentations and specialized firewall architectures (Gira F1 Bridge). Implemented low-level, hardware-adjacent IoT sensor logic for device-context awareness, including proximity detection for automated display wakeup/dimming and the end-to-end architecture of an automated, adaptive day/night mode driven by ambient light sensors. Designed a server-driven UI configuration engine where layout definitions, control states, heating/blinds telemetry, and statistics were dynamically parsed, bound, and rendered from the Gira HomeServer backend. Engineered a resilient offline-first architecture to guarantee uninterrupted operation during network outages, featuring local state persistence, background reconciliation queues, and automated UI re-configuration upon server reconnection. Executed a critical legacy migration of the push notification infrastructure from Google Cloud Messaging (GCM) to Firebase Cloud Messaging (FCM), alongside deep structural modularization to eliminate tight coupling, resolve concurrency bottlenecks, and streamline complex inter-process and inter-module communication.

Software: Android, Java, Kotlin, Rest, Web service

Project management: CI/CD, Confluence, GIT, Gradle, Jenkins, Jira, Scrum, SVN

Period: 01.10.2018 – 31.08.2020

Museum application for interactive visitor communication…

Client/end customer: Museumsverein Morsbroich e.V.

Project: Design of an interactive visitor communication app on industrial PCs. Implemented a system lockdown for 24/7 operation, a local editorial backend with auth and bad-keyword filters, real-time input sanitization, and automated dynamic beamer projection.

Description: Architecture and comprehensive development of an interactive visitor communication and moderation platform running on secured industrial touch PCs and kiosk hardware. Engineered a robust, custom Android system lockdown to guarantee secure 24/7 public exhibition operation. Designed a hidden, local editorial backend featuring two-tier authentication (Admin/Editor roles), a configurable bad-keyword filter, and dynamic styling options. Implemented advanced, real-time input sanitization directly within the edit fields (blocking emojis, repetitive special characters like *, and excessive whitespace while preserving manual line breaks and text length limits) alongside multi-language support (including Arabic layout handling via Google Keyboard). Developed an automated dynamic scaling and projection algorithm that outputted approved visitor comments via beamers as visual text blocks, inversely scaling font sizes relative to text length for optimal legibility. ​Software: Android, JetPack, JetPack Compose, Kiosk Lockdown, Kotlin, Multi-threading, XML, Custom Input Filtering, Dynamic UI Scaling

Software: Android, JetPack, JetPack Compose, Kiosk system, Kotlin, Threads, XML

Period: 07.05.2025 – 14.08.2025

DHL Android App…

Client/end customer: DHL Paket GmbH

Project: Enhancement of the enterprise delivery driver app on Zebra handhelds with a primary focus on tracking down and fixing rare, critical bugs. Handling offline-online state synchronization, route management, locker workflows, and Bluetooth label printing via ZPL/CPCL.

Description: Further development, stabilization, and architecture optimization of the mission-critical DHL delivery driver application running on Zebra handheld devices. Focused on mastering complex, real-time data flows within a sophisticated multi-threading environment. Responsibilities included robust handling of live barcode scans, seamless offline-online state synchronization, dynamic route management, and logistics workflows for servicing and filling DHL service point lockers. Additionally, implemented a stable print history and reprint mechanism communicating directly via Bluetooth with mobile label printers utilizing text-based ZPL/CPCL print commands.

Software: Android, Android Koin, JetPack, JetPack Compose, JSON, Junit Tests, Kotlin, Interface specification, Threads

Hardware: Bar code

Project management: Confluence, GIT, Gradle, Jira

Period: 01.02.2026 – 15.06.2026