Hendrik Levering
Senior Modernization Engineer – Legacy Web App Performance & Refactoring (Energy Sector)
Experience
Senior Modernization Engineer – Legacy Web App Performance & Refactoring (Energy Sector)
Levering IT GmbH
Re-architected a web application that had grown over years, modularizing tightly coupled components
Reduced response times from several seconds to <50 ms
Removed performance bottlenecks
Simplified architecture so internal teams can implement features on their own again
Senior Backend & Integration Engineer – Legacy Web App and IoT Integration (Energy Sector)
Levering IT GmbH
Modernized an existing platform and built a simple, robust data flow to connect distributed customer systems to an IoT backend
Simplified Kafka/MQTT pipelines and removed duplicates
Expanded observability for reliable near-real-time monitoring and a foundation for predictive maintenance
Lead Developer – SaaS Editor for Organic Shapes (G-Code Generator)
Levering IT GmbH
Developed a browser-based editor with its own slicing engine that enables organic single-wall shapes, checks manufacturability, and generates G-code for 3D printing
Designed a small, easy-to-understand platform with a K3s cluster, Git-based deployments, and observability
Implemented a functional UI for low operational load and easy extensibility
Senior Backend Engineer – Platform for Ecosystem Analysis (Environmental Engineering)
Levering IT GmbH
Built a scalable yet simple backend for asynchronous, long-running compute jobs and external data sources to replace loose script collections
Introduced clear data models and APIs (REST/GraphQL) to simplify onboarding and reduce operational incidents
Owner & Principal Consultant
Levering IT GmbH
Modernized legacy systems, automated and digitized business processes
Developed web-based enterprise applications and internal tools
IT consulting including technical due diligence, system audits, and architecture coaching
Senior Engineer – Expert Suite Usability & Automation (Energy Sector)
Levering IT GmbH
Improving usability and robustness of complex expert software against misuse
Automating manual process chains
Focus on refactoring, CI/CD, and eliminating unnecessary steps in core workflows
Software Developer / Senior Consultant
Siemens / Siemens Energy AG
Development of internal web and desktop applications
Migration of legacy code and data modeling
Building CI/CD pipelines and automation
Conducting internal Python training in the industrial and energy sector
Developing automation tools and NX plug-ins (C#, Python) for parametric CAD models and simulation workflows
Establishing script-based pipelines to optimize manufacturing processes, increasing throughput and process reliability
Industries Experience
See where this freelancer has spent most of their professional time. Longer bars indicate deeper hands-on experience, while shorter ones reflect targeted or project-based work.
Experienced in Energy (11 years), Manufacturing (11 years), Information Technology (5 years), and Professional Services (5 years).
Business Areas Experience
The graph below provides a cumulative view of the freelancer's experience across multiple business areas, calculated from completed and active engagements. It highlights the areas where the freelancer has most frequently contributed to planning, execution, and delivery of business outcomes.
Experienced in Information Technology (13 years), Production (9 years), Quality Assurance (7 years), and Product Development (3 years).
Summary
Hendrik Levering is a Senior Software Engineer and consultant with over 10 years of experience in modernizing complex, mission-critical systems in energy, industrial, and SaaS environments. He specializes in transforming slow, fragile legacy platforms into clear, high-performing, and maintainable systems – using functional principles, Python, and Clojure. Companies hire him when architecture and infrastructure have spun out of control, response times are measured in seconds, or teams are stuck in over-engineering and slow processes. Hendrik cuts away unnecessary complexity, designs simple data models and system boundaries, and builds internal tools, editors, and automation that drastically simplify development and operations.
Skills
- Legacy Modernization & Refactoring Of Large, Long-lived Systems (Monoliths, Old Web Apps, Desktop Tools, Scripts)
- Performance Engineering (Several Seconds → <100 Ms)
- Simplifying Overloaded Cloud/infrastructure Landscapes (Aws/azure → Focused, Lean Setups)
- Functional Data Modeling, Clear Domain Boundaries, Event-driven Data Flows
- Building Internal Tools, Editors & Automation Systems That Free Up Developer Time
- Lean Ci/cd Pipelines With Short Feedback Loops (Github Actions / Gitlab Ci)
- Technical Due Diligence, System Audits, Architecture Consulting & Team Coaching Through The Modernization Process
- Backend: Python, Clojure, Fastapi, Datomic, Postgres
- Frontend: Clojurescript, React, Vue.js
- Infra: Hetzner, Docker, K3s, Lightweight Kubernetes, Caddy, Linux
- Dev Practices: Functional Programming, Repl-driven Development, Tdd/bdd, Property-based Testing, Solid, Ddd, Clean Code, Continuous Delivery
- Also Experienced With (Used When Needed): Java, C#, Typescript, Node.js, Kafka, Mqtt, Redis, Mongodb, Aws, Azure, Terraform, Devops, Gitops
- Python
- Python2
- Python3
- Senior Python Developer
- Lead Python Engineer
- Clojure
- Clojurescript
- Functional Programming
- Repl-driven Development
- Fastapi
- Django
- Flask
- Microservices
- Legacy Modernization
- Refactoring
- Performance Optimization
- Architecture
- Solution Architect
- Software Architect
- Clean Architecture
- Simplicity-first
- Cloud Migration
- Aws
- Azure
- Kubernetes
- K3s
- Docker
- Ci/cd
- Github Actions
- Gitlab Ci
- Postgres
- Datomic
- Rama
- Graphql
- Rest
- Event-driven
- Kafka
- Mqtt
- Iot
- Internal Tools
- Developer Productivity
- Automation
- Editors
- Computational Systems
- Saas
- B2b Saas
- Energy Sector
- Industrial Iot
- Environmental Engineering
- Consulting
- Technical Lead
- Lead Engineer
- Principal Consultant
- Freelance
- Contractor
- Sql
- Postgresql
- Llm
Languages
Education
Dual IHK apprenticeships as Industrial Mechanic · Industrial Mechanic · Germany
Westfälische Hochschule
M.Eng. Mechanical Engineering · Mechanical Engineering · Germany
Universität Duisburg-Essen
Supplementary studies · Applied Computer Science · Essen, Germany
Profile
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