GraphQL Experts in Hamburg

• Designed and implemented a Python-based ETL pipeline with the Dagster framework to transform raw energy data from heterogeneous sources using InfluxDB and visualizations in Grafana
• Defined time-based and dependency-based jobs
• Deployed to managed Kubernetes clusters using Helm
• Integrated InfluxDB Cloud
• Prepared data for use in Grafana, including cleaning, normalization, and time-based resampling in Python
• Developed dashboards and visualizations in Grafana
• Developed unit tests with mocking using pytest
• Set up a CI/CD pipeline in GitLab

Technologies: Python, Dagster, InfluxDB, Grafana, pandas, pytest, REST, CI/CD, GitLab, Container, Kubernetes, Helm, Docker, Cloud

traigo is VTG's digital rail logistics and fleet management platform. It processes large volumes of telemetry, mileage, geofence, sensor and wagon-movement events in near real time and provides operational services for rail logistics customers across Europe.

As part of Team Customer Selfcare, I worked on the design, implementation, optimisation and operation of large-scale backend services and event-driven processing pipelines — covering both feature development and operational ownership of business-critical production systems. I also regularly acted as first responder for production incidents, data inconsistencies and performance investigations across multiple distributed services.

• Design and implementation of event-driven backend services.
• Migration and replacement of legacy processing pipelines.
• Development of replay / rebuild mechanisms for large event datasets.
• High-throughput asynchronous event processing on SNS / SQS.
• Database and query optimisation for PostgreSQL and DynamoDB.
• Design of scalable read / write models and aggregation pipelines.
• Production troubleshooting and operational support.
• Performance tuning and infrastructure scaling.
• Design and stabilisation of integration and system tests.
• Technical concepts, architecture documentation, and cross-team collaboration.
• Support the further development of existing GitLab CI/CD pipelines

Geofence & Wagon Stay Processing

• Algorithm to detect vehicles within geofences (entry, exit, dwell time).
• Event sourcing with guaranteed chronological order within the affected time window.
• Refactored geofence event and wagon-stay processing logic for performance.
• Resolved race conditions and event-ordering problems in distributed services; server-side filtering, aggregation and optimised query pipelines.
• Repair and replay tooling for corrupted or inconsistent movement data.

Fleet Metadata & Mileage

• Modernised the service; migrated storage from DynamoDB to PostgreSQL to improve traceability and accelerate new features.
• Scalable mileage aggregation and replay mechanisms.
• Read / write models and optimised queries for high-volume mileage calculations.

Sensor & Telematics Integration

• Integrated telemetry and sensor processing pipelines.
• Snapshot and state-calculation logic for sensor systems.
• APIs and persistence models for wagon sensor data; data-quality improvements.
• Further development of a service using gRPC for intra-service communication.

Movement Segment Processing & Routing

• Migrated services to new movement-segment event streams.
• Built replay and rebuild tooling for segment correction.
• Optimised throughput and reliability for high-volume event processing.

Condition Monitoring & Wagon Analytics

• APIs and backend services for wagon condition monitoring.
• Brake-wear prediction processing and wagon analytics functionality.
• PostgreSQL views and optimised query models for operational dashboards.

Operational Reliability - First Responder

• Investigated production incidents and distributed-system failures; DLQ analysis, replay and operational recovery.
• Tuned database performance and AWS infrastructure under production load.
• Improved observability, monitoring and operational tooling.
• Supported rollout strategies, monitoring and post-deployment stabilisation.

• Environment: AWS, Ruby on Rails, GraphQL, React Native
• Penetration test for Backend, Android-App and iOS-App

• Restructuring for product-led growth in the field of digital user-centric tech product development language learning experiences
• Scaling empowered tech product teams
• Anti-fragile software engineering

• Integration of SAP Commerce Cloud with SAP Cloud for Customer
• Creation and execution of unit and integration tests
• Error analysis and bug fixing

• Significant enhancement of the B2B React SPA software "opti.node" for commercial operations management for renewable energy plant operators
• Introduced features not previously available on the market, resulting in a significant revenue increase
• Comprehensive automated tests within Storybook
• Introduced a UI library to improve developer experience and speed up feature development by about 40%
• Clear presentation of complex commercial and legal issues, with intuitive UX and UI
• UX consulting to shorten essential interaction flows by 75%

Expomate platform

• Built a cross-platform exhibitor inquiry management app using React Native and RoR 8, leveraging RESTful APIs, Solid Queue for background job processing, and Devise for authentication on the backend, with Redux and AsyncStorage for state management and local data persistence.

TaskINT platform

• Developed a unified platform for task execution, time tracking, invoicing, client relations, and staff management using RoR 8 and React.js, utilising RESTful APIs, Sidekiq for background jobs, and Zustand for state management and WebSockets for real-time data sync, with 300+ users onboarded across 5 clients.

• Solution for micro-service and frontend solution for the electric grid
• Leading of development teams
• Technologies: React-Native, TypeScript, Kotlin, AWS, Infrastructure As Code, Serverless Architecture, React, NoSQL, GraphQL, Angular, Playwright, Python, ML(Ops), Kubernetes, Docker

• Development of a CMS-based online platform as a central hub for multimedia brand communication, focusing on accessibility, web performance, and data protection.
• Technologies: PHP, Craft CMS, Twig, HTML, CSS, JavaScript, Alpine.js, htmx.

• Role: Developer, Architect
• Technologies: java, typescript, golang, spring (boot, web, security, data), Angular, AWS (OpenSearch, Aurora, SNS/SQS, CloudWatch, EC2, IAM), Kubernetes, Terraform, Helm, OAuth, Keycloak, CI/CD, gradlew, Liquibase, Test Driven Development, shell scripting

• Built scalable and reliable web using React, TypeScript, JavaScript and open-source tooling, taking full ownership from development to deployment with minimal oversight
• Translated client requirements and visual designs into functional, user-friendly interfaces by applying UI/UX design principles, ensuring the delivered product aligned with the client's product vision
• Proactively identified and resolved complex technical issues spanning frontend and DevOps (AWS), going beyond the defined scope to ensure continuous and stable delivery, with test coverage maintained via Jest

• Extended the document management system with a standard CMIS (Content Management Interoperability Services) interface
• Implemented CMIS core services like navigation, access rights, search, CRUD operations, and versioning in Java
• Implemented based on RESTful / OpenAPI services
• Delivered as a fat-jar and native container image
• Deployed on-premises and serverlessly as an Azure Container Application using Terraform
• Improved team autonomy through infrastructure engineering and short feedback loops
• Established observability with OpenTelemetry, Azure Monitor, and Azure Logic Apps
• Introduced Terraform and trunk-based development processes
• Ensured quality with BDD tests in C# using SpecFlow and Testcontainers
• Created Azure DevOps pipeline integration tests
• Introduced cloud deployment processes
• Trained staff in cloud and Terraform

• Migration of 3 DE/AT payment iOS/Android apps and web portal to global solution
• Performed a fit gap analysis for 6 consumer apps vs. global solution
• Managed the migration project to global CWC solution, developed end-to-end tests for backend systems, Pi Planning, release planning

• Reimplementation of the ESN.com online shop with Shopify's Hydrogen and Remix
• Headless CMS Contentful integration via GraphQL