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.

My work rests on collaboration (working with teams and clients), reliability (taking ownership and delivering results), and transparency (clear, efficient communication and high availability).

To work with me you can find me on LinkedIn (opens in a new tab), or reach out via eMail.

Software Engineering

I work with legacy code, lead architecture modernizations (Java-to-Kotlin migrations, backend and HTTP client migrations, XML views to Jetpack Compose), and improve test coverage and maintainability where needed. I also start greenfield projects and build a shared vision with stakeholders. Feature development and tech debt compete for resources, so I keep business objectives first.

I work with test-driven development, clean architecture, and continuous integration/delivery, and treat user interface and experience design as part of the development cycle.

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 translate between business and tech, mentor engineers, and share knowledge through pair and ensemble programming and demos.

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

Engineering services offered:

  • Build native or Kotlin Multi­platform mobile apps and features
  • Migrate to Kotlin Multiplatform (KMP, KMM)
  • 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)) and predictive project management (waterfall), and pick the approach that fits the project.

As a technical product owner I practice continuous discovery: keeping the product vision clear with stakeholders and letting user research inform development, so the result meets both business and user needs.

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. The goal is shared understanding and decisions teams can act on.

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

Creation and facilitation of single or multiple workshops:

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.