Kotlin Experts in Dusseldorf
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Meet FRATCH Experts in Dusseldorf, who have recently used Kotlin
Boris Solos
Last position:
Generalist expert for software development at Mercor
- Training the AI models, evaluating images and texts for UI/UX, turning the provided data into insights via OpenAI Feather as part of the machine learning workflow
Technologies: OpenAI Feather
Marc Smyk
Last position:
Fullstack Developer at PLANT-MY-TREE
PLANT-MY-TREE®-per-order
The application enables Shopify merchants to automatically place tree-planting orders for every incoming order. By integrating ecological contributions directly into the purchase process, the manual effort for tracking and billing reforestation initiatives is eliminated. The system increases transparency for end customers through real-time visualizations of the ecological impact directly in the storefront. The architecture is based on a modular monolith with Spring Boot in the backend and an integrated React app inside the Shopify admin area. The solution uses webhooks to capture order data in an event-driven way and integrates the weclapp ERP system for automated monthly invoicing. An app proxy mechanism provides dynamic statistics such as CO2 compensation and planted trees without any performance loss for the merchant shop.
Tasks:
- Design of the modular software architecture based on Spring Modulith to ensure high maintainability
- Development of the event-driven business logic for evaluating Shopify orders via webhooks
- Implementation of automated invoicing by connecting the weclapp REST API
- Building the frontend using React Router and Shopify App Bridge for native integration
- Design of the database model and implementation of the persistence layer with JPA/Hibernate and Prisma
- Integration of internationalization processes for global use in the frontend and email communication
- Automation of deployment processes using Docker and GitLab CI/CD
Project skills: Java 25, Spring Boot, Spring Security, Spring Modulith, Hibernate, JPA, REST API, PostgreSQL, Maven, Liquibase, React, TypeScript, React Router, Vite, Node.js, Prisma, Zod, Docker, Docker Compose, GitLab CI/CD, Shopify CLI, Shopify App Bridge, Polaris, weclapp, i18next, Lombok, Vitest
Jan Kronenberg
Last position:
Software Architect: Training Platform for IT Career Changers at appvanced
- Mobile: Kotlin Multiplatform (KMP), Kotlin, Swift, SwiftUI, Jetpack Compose, Ktor, Room, Koin
- Backend: Spring Boot, GCP Cloud Run, GCP Load Balancer, GCP Eventarc
- Planned and developed a cloud backend architecture with Google Cloud Platform
- Developed a cross-platform architecture with Kotlin Multiplatform (KMP)
- Tech lead for comprehensive large project including webshop, two apps and omnichannel backend
Jan G.
Last position:
Master Data Application at confidential
Visualization, search, and maintenance of various types of master data, providing them via a REST API, and implementing a variety of import and export formats.
Implementation, architecture, project management.
Technologies and tools: Angular (Signals, Signal Store, swagger-codegen, standalone components), Java, PostgreSQL, ActiveMQ, JavaScript, Spring Boot (Spring Core, Spring MVC, Spring Data/JPA via Hibernate, Spring Security, Spring Modulith), JUnit, Flyway, QueryDSL, GraphQL, REST API, Node, npm, Maven, SonarQube, GitLab CI/CD pipelines, Docker, Nexus, OpenAPI + Swagger UI, Keycloak, OAuth2, OpenID Connect, IntelliJ IDEA, Jira, Confluence.
Peter Hiebl
Last position:
Product Owner / Senior Business Analyst at Freelance management consultant
- Analysis of the possibility of extracting market location data into a separate microservice within an overarching web portal
- Developing a more user-friendly target process based on the current process in coordination with the users
- Coordinating the related architecture concept with architects and developers
- Aligning the related epics and user stories with the relevant departments
- Backlog prioritization and project planning (incl. effort estimation)
- Testing and accepting the implemented user stories
- Technologies/Tools used: MS Office, Jira, Mural, Kotlin, React, GitHub, MS Azure, SQL, Postman, XML, JSON, Kafka, Balsamiq, BPMN
Jacqueline Haefke
Last position:
Kitchen Appliance Manufacturer
Setting up and enhancing an international subscription management system
Migrating and decommissioning a Hybris-SAP system and integrating Zuora
Implementing numerous interfaces to various systems (external and internal)
Setting up and improving monitoring with Grafana, Prometheus, and Databricks
Introducing logging with Loki
Implementing business requirements using jQuery, Thymeleaf, Spring Boot, Java, Go, and Python
Adjusting and extending the GitLab CI pipelines
Setting up and extending infrastructure as code with Terraform and ArgoCD on AWS
Setting up and running E2E and performance tests
Expanding the Databricks business intelligence solution to provide various KPIs
Responsibilities: Architecture, DevOps, development, unit tests, coaching employees and apprentices, E2E, smoke, and integration tests, agile methods consulting (Kanban, Scrum)
Technologies and methods: Java, Go, Kotlin, Node.js, Spring Boot, SOAP/REST, Quarkus, Thymeleaf, Vaadin, Slack, Jira, Confluence, IntelliJ, GitLab, SQS, Kafka, AWS, Kubernetes, Terraform, Maven, Gradle, GitLab CI, Databricks
Philip Strauß
Last position:
Web Developer at Self-employed Web Developer
- Self-employed Web Developer
- Website: [link]
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Statistics of experts using Kotlin
Aggregated from the professional profiles of matched freelancers.
Experience
12 years (Germany: 17 years)
Position duration
1.2 years (Germany: 2.7 years)
Positions per freelancer
13 (Germany: 12)
Top business areas
Information Technology, Product Development, Business Intelligence
Top industries
Information Technology, Banking and Finance, Transportation
Certification focus areas
Information Technology, Product Development, Project Management
Bachelor's degree or higher
75% (Germany: 93%)
Master's degree or higher
50% (Germany: 57%)
Certifications per freelancer
1 (Germany: 2)
Most common languages
German, English, Polish
Speak two or more languages
100% (Germany: 98%)
Based on our profile pool as of 30 Aug 2026.
Daily rate distribution
The chart shows how the daily rates of freelancers in this technology in Dusseldorf are distributed, based on recent contracts on our platform. Each bar covers a rate range — its height shows how many freelancers charge within that range.
Average rates of experts in Dusseldorf using Kotlin
Rates are based on recent contracts and do not include FRATCH margin.
The average daily rate is the mean of all daily rates from recent contracts of comparable freelancers on our platform.
The median daily rate is the middle value of all daily rates — half of comparable freelancers charge less, half charge more. Unlike the average, it is barely affected by outliers.
Calculated based on our freelancers’ daily rates as of 30 Aug 2026. Actual rates may vary depending on seniority level, experience, skill specialization, project complexity, and engagement length.
About the technology
Kotlin for modern software
Kotlin is a statically typed language used to build backend services, Android apps, shared libraries, and tooling. It runs on the JVM and also targets JavaScript and native code when a project needs it. Companies choose Kotlin when they want concise code, strong safety, and smooth work with existing Java systems.
Where Kotlin fits
Kotlin shows up in product teams, platform work, and mobile delivery. It is a strong fit for:
- API services and microservices
- Android app features and UI layers
- Shared business logic between mobile and backend
- Migration from Java codebases
- Build scripts with Gradle Kotlin DSL
Ecosystem and tooling
Strong Kotlin specialists work comfortably with the wider JVM stack. That includes Spring Boot, Ktor, Gradle, JUnit, Coroutines, and serialization tools. They know when to use idiomatic Kotlin and when to stay close to Java for easier team adoption.
When companies bring in help
Freelance expertise helps when a team needs to start a Kotlin codebase, rescue a rushed migration, or move a mobile app toward cleaner architecture. It also helps when Dusseldorf teams need short-term support for delivery spikes, legacy cleanup, or cross-functional work with Java and Android specialists.
What strong professionals deliver
A good Kotlin professional writes code that is readable, testable, and easy to maintain. They pay attention to null safety, coroutine use, error handling, and boundaries between domain logic and framework code. You should expect clear pull requests, practical guidance, and fewer surprises in production.
How to assess fit
Look for real delivery across the parts that matter in your project.
- Production Kotlin work, not only tutorials
- Clean use of Coroutines and structured concurrency
- Solid testing with unit and integration coverage
- Experience with JVM systems or Android, as needed
- Clear communication with your in-house specialists
Frequently asked questions
Need clarity? These are the questions we hear most often about Kotlin.
Kotlin is used for Android apps, backend APIs, shared business logic, and internal tools. It is especially useful when a team wants concise code that still fits well into a JVM-based system. Many companies also use it for modernizing Java projects without rewriting everything at once.
Kotlin often gives teams more expressive code, safer null handling, and better support for coroutines. Java still matters when a codebase is already built around it, but Kotlin can reduce boilerplate and speed up feature work. The best choice depends on the current stack, the team’s habits, and how much migration is realistic.
No. Kotlin is popular on Android, but it is also widely used for server-side systems, shared libraries, command-line tools, and build logic with Gradle Kotlin DSL. A strong freelancer should be able to move between mobile and backend work when the project calls for it.
A Kotlin specialist often needs solid JVM knowledge, Spring Boot or Ktor experience, testing habits, and a good feel for Gradle. For mobile work, Android, app architecture, and API integration matter too. Coroutines, serialization, and dependency injection are also common parts of the stack.
A Kotlin project can benefit from freelance help as soon as there is a real codebase, a migration plan, or a deadline that needs focus. Early support is useful for setup and architecture decisions, while later support is often about delivery, refactoring, or bug fixing. The right level depends on how risky the code path is and how much team knowledge already exists.
Yes. Kotlin work is often well suited to remote collaboration because most tasks live in code review, tests, and clear issue tracking. In Dusseldorf, some teams still prefer on-site sessions for architecture workshops or kickoff meetings, then continue delivery remotely.
A strong Kotlin expert leaves behind readable code, useful tests, and decisions that your team can maintain. Look for examples of production work, not just sample apps, and ask how they handle null safety, coroutines, and Java interoperability. Good communication matters as much as syntax knowledge.
A Kotlin assignment may involve greenfield development, migration from Java, Android feature work, or fixing architecture debt. Freelancers should expect to explain trade-offs clearly and work with existing conventions where needed. The best projects give enough context to let them improve the code without disrupting delivery.
The average hourly rate of freelancers in Dusseldorf, Germany who have used Kotlin in their recent projects is 87 €, which corresponds to a daily rate of about 693 € based on an 8-hour working day.
Of the freelancers in Dusseldorf, Germany who have used Kotlin in their recent projects, 75% hold at least a Bachelor's degree and 50% hold at least a Master's degree.
On average, freelancers in Dusseldorf, Germany who have used Kotlin in their recent projects have 12 years of professional experience, with a single engagement typically lasting around 1.2 years.
The most common languages among freelancers in Dusseldorf, Germany who have used Kotlin in their recent projects are German (100%), English (100%), and Polish (14%).
The most common industries among freelancers in Dusseldorf, Germany who have used Kotlin in their recent projects are Information Technology (100%), Banking and Finance (43%), and Transportation (43%).
The most common business areas among freelancers in Dusseldorf, Germany who have used Kotlin in their recent projects are Information Technology (100%), Product Development (100%), and Business Intelligence (71%).
Main locations of FRATCH Experts, who have recently used Kotlin
Our freelancers and interim experts are at home across the DACH region — available on-site in the major business hubs or fully remote. Choose a location to discover matched specialists, local market insights and up-to-date availability.
Berlin 
Hamburg 
Munich 
Cologne 
Frankfurt Request a free demo
Get in touch with the FRATCH team and we will get back to you within 4 hours.
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Philipp Thomaschewski
FRATCH CEO
