Mario Völker (M. Sc.) | Freelance

Portrait of Mario Völker

With 12+ years of experience in software engineering in industries like automotive, finance, eCommerce, telecommunications, and entertainment, I have shipped 30+ apps and led projects in large corporations and start-ups. I am available for long-term engagements and time-critical, resource-bound projects.

I am based in Berlin and work remotely. On-site work and travel are possible.

Software Engineering

I work with legacy code, lead architecture modernizations, and start greenfield projects, building a shared vision with stakeholders either way. Feature development and tech debt compete for resources, so I keep business objectives first. I work test-driven, with clean architecture and continuous delivery, and share knowledge through pair and ensemble programming.

I build robust, secure systems (OAuth2, obfuscation) across the full stack: backend services (Spring Boot), serverless architecture (AWS), and API design (gRPC, REST) in Kotlin and Java. This includes working with legal teams on GDPR and EU Data Act compliance.

I work with: Kotlin, SQL, Dagger2/Hilt/Koin, Jetpack Compose, XML, OpenAPI, Spring Boot, Figma. My focus is mobile: Kotlin Multi­platform (KMP), native Android, and iOS (Swift).

Engineering services offered

  • Build native or Kotlin Multi­platform mobile apps and features, or migrate existing apps to KMP
  • Migrate to AndroidX Jetpack Compose and Design Systems (Figma), with focus on the European Access­ibility Act (EAA, Barriere­freiheits­stärkungs­gesetz/BFSG)
  • Migrate Java to Kotlin (including RXJava)
  • Increase (unit) test coverage
  • Mentor junior developers and teams on engineering best-practices
  • Review and evaluate existing apps or proposals

Agile and classic IT project management

I manage projects with agile methods (Kanban, Scrum, Scaled Agile Framework (SAFe)) or predictive project management (waterfall), whichever fits the project. As a technical product owner I keep the product vision clear with stakeholders and let user research inform development.

Project management services offered

  • Technical product ownership with continuous discovery and data-driven decision-making
  • Project management with predictive or agile methods
  • Strategic planning, business analysis, feasibility studies

Workshop facilitation

I create and facilitate workshops, as part of an engagement or standalone: EventStorming (Domain-Driven Design (DDD)), Design Thinking, and classic requirements elicitation and business analysis.

Trained at the HPI School of Design Thinking; EventStorming Masterclass (Avanscoperta).

Workshops and trainings offered

References (excerpt)

Several of these client relationships have lasted more than ten years.

Work with me

You can find me on LinkedIn (opens in a new tab), or reach out via eMail.