Kotlin Experts in Düsseldorf
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Meet FRATCH Experts in Düsseldorf, who have recently used Kotlin
Boris S.
Last position:
Generalist expert for software development at Mercor
- Training AI models, evaluating images and text UI/UX, turning the provided data into insights through OpenAI Feather as part of the machine learning workflow
Technologies: OpenAI Feather
Marc S.
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
Peter H.
Last position:
Product Owner / Senior Business Analyst
- Analysis of the possibility of transferring market location data to a separate microservice in an overarching web portal
- Development of a more user-friendly target process based on the current process in coordination with users
- Coordination of the related architecture concept with architects/developers
- Coordination of the related epics and user stories with the relevant business departments
- Backlog prioritization and project planning (including effort estimation)
- Testing and acceptance of implemented user stories
- Technologies/tools used: MS Office, Jira, Mural, Kotlin, React, GitHub, MS Azure, SQL, Postman, XML, JSON, Kafka, Balsamiq, BPMN
Jan K.
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.
Jacqueline H.
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 S.
Last position:
Web Developer at Self-employed Web Developer
- Self-employed Web Developer
- Website: [link]
Discover over 15,000 top freelancers
Statistics of experts using Kotlin
Aggregated from the professional profiles of matched freelancers.
Experience
12 years (Germany: 17 years)
Position duration
1.5 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: 55%)
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 29 Oct 2026.
Daily rate distribution
The chart shows how the daily rates of experts in this technology in Düsseldorf are distributed, based on recent contracts on our platform. Each bar covers a rate range — its height shows the share of experts charging within that range.
Average rates of experts in Düsseldorf 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 29 Oct 2026. Actual rates may vary depending on seniority level, experience, skill specialization, project complexity, and engagement length.
Kotlin experts industry focus
See which industries our matched freelancers work in most often — every figure is calculated live from the freelancers on FRATCH.
- Information Technology (100%)
- Banking and Finance (43%)
- Transportation (43%)
- Manufacturing (43%)
- Retail (43%)
- Agriculture (29%)
- Construction (29%)
- Insurance (29%)
Please note that freelancers can work across multiple industries, so percentages overlap.
About the technology
Kotlin in practice
Kotlin is a statically typed language from JetBrains for the Java Virtual Machine, Android and multiplatform software. Its concise syntax, null-safety features and interoperability with Java make it suitable for modern applications without discarding established Java libraries. Teams use it for mobile apps, backend services, shared business logic and developer tools.
Products and platforms
Kotlin supports Android applications, web backends, cloud services and cross-platform products. Kotlin Multiplatform lets teams share selected code across Android, iOS, desktop and server environments while keeping platform-specific interfaces where needed.
- Android applications with Jetpack Compose
- Backend APIs and services with Ktor or Spring
- Shared domain logic with Kotlin Multiplatform
- Asynchronous workflows using coroutines and Flow
Ecosystem and tooling
Strong Kotlin specialists work across the language, its standard library and the JVM ecosystem. Their toolkit may include Gradle, IntelliJ IDEA, Android Studio, Jetpack libraries, Ktor, Spring Boot, kotlinx.serialization and testing frameworks such as JUnit. They also understand Java interoperability, dependency management and release automation.
Good implementation depends on more than syntax. Professionals structure modules clearly, manage coroutine lifecycles, handle errors deliberately and keep APIs, data models and build pipelines maintainable.
When companies bring in specialists
Freelance Kotlin expertise is useful when an Android product needs modernization, a Java service is being migrated or a new backend must launch with a coherent architecture. Specialists can also help teams evaluate Kotlin Multiplatform, stabilize asynchronous code or extend an existing product without slowing internal delivery.
- Rework legacy Android screens with Jetpack Compose
- Introduce shared code across mobile platforms
- Design and test Kotlin APIs
- Improve build, release and observability workflows
Düsseldorf delivery context
Companies in Düsseldorf often combine mobile products, connected services, commerce systems and enterprise software. Kotlin specialists can work remotely or join on-site sessions for discovery, architecture reviews and team enablement. Agreeing early on language expectations, collaboration hours and access to internal systems keeps distributed work effective.
What strong professionals bring
A strong Kotlin professional explains trade-offs instead of treating the language as a shortcut. Look for experience with production Android or JVM systems, thoughtful coroutine and concurrency design, automated testing and measurable attention to security, performance and accessibility.
Ask for examples of decisions involving Java integration, module boundaries and failure handling. The best specialists adapt to an existing codebase, document their reasoning and leave the team with patterns it can maintain after the engagement.
Frequently asked questions
Need clarity? These are the questions we hear most often about Kotlin.
Kotlin is used for Android applications, backend services, command-line tools and shared code across mobile platforms. It runs on the JVM and can also target JavaScript and native environments, making it useful when a product spans several platforms.
Kotlin offers null safety, concise syntax, extension functions and coroutines while remaining interoperable with Java. Java may still be the practical choice when a team relies heavily on existing Java conventions or libraries, but both can share a codebase.
Kotlin Multiplatform is useful when mobile teams want to share domain logic, networking or data handling without forcing identical user interfaces. A specialist should first assess platform differences, release processes and the amount of code that genuinely benefits from sharing.
A strong Kotlin freelancer may also bring Android and Jetpack Compose expertise, Java, Gradle, SQL, REST or GraphQL, cloud services and automated testing. For cross-platform work, knowledge of Swift, iOS conventions and Kotlin Multiplatform is especially relevant.
The required Kotlin experience depends on the risk and scope of the work, not on the language alone. A small feature may need focused implementation skills, while a migration or shared-platform strategy calls for proven architecture, testing and release experience.
Kotlin work is well suited to remote collaboration when repositories, environments and product decisions are documented. Düsseldorf teams should align on communication language, working hours, security access and regular architecture sessions before delivery begins.
Review how a Kotlin specialist handles nullability, coroutine cancellation, API boundaries, tests and build configuration. Ask for a walkthrough of a comparable production decision and check whether the code is readable, observable and easy for the internal team to extend.
Kotlin works well for backend APIs and services through frameworks such as Ktor and Spring Boot. Its Java compatibility, coroutines and mature JVM tooling make it a practical option, provided the team also plans for monitoring, deployment, security and operational support.
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 695 € 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 1.5 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 
Stuttgart 
Dortmund Request a free demo
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FRATCH CEO
