Kotlin Experts in Cologne
in minutes from over 15,000 CVs with the power of AIHire experts who build Kotlin services, Android apps, and shared code with Kotlin Multiplatform. Get specialists who work with Coroutines, Spring Boot, and the JVM stack, matched fast and precisely from vetted, available freelancers.
Meet FRATCH Experts in Cologne, who have recently used Kotlin
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
Thomas Pawlitzki
Last position:
Freelance Software Architect at Self-employed
Ayhan Gezer
Last position:
Senior QA Engineer / Test Automation Engineer / SDET at Rewe digital
Consulting, designing, and implementing the software testing lifecycle for multiple Android apps and backends Introducing test automation with Appium, SpringBootTest, RestAssured Setting up and managing emulators Developing an E2E library, an integration library, a Testcontainers library, and other libraries Developing, implementing, and advising on CI strategies Building the test environment with Testcontainers and virtualization Developing and implementing test cases for integration tests and end-to-end tests Establishing a maintainable test architecture with low entry barriers to simplify the creation of automated tests Some tools and technologies used: JUnit, RestAssured, Testcontainers, Kubedock, Appium, Android emulator, Jira Xray, Mockito, WireMock, Spring Framework, Kotlin
Andreas Ernst
Last position:
Consultant at Iteratec GmbH
Predrag Perovic
Last position:
Test Developer | Test Automator at CreditReform
Technologies: Java 25, Selenium, Insomnia, SSO, GitLab, Jenkins, Docker, Kubernetes, Jira, IntelliJ, Nexus, Oracle, MariaDB, Spring Boot, Grafana, Concept Board, Vue.js, OpenAPI, Kotlin. Implementation, maintenance, and extension of automated end-to-end regression tests for UI and API interfaces. Appropriate and targeted test automation across multiple software products, including Java-based Windows applications. Automating business processes with Selenium, reset jobs, and DB import jobs, as well as creating test concepts, test case descriptions, and structured bug reporting.
Louis Nguenkam
Last position:
Specialist in Adobe Experience Manager & Microservices at Nguenkam Consulting & Engineering
Java 11/21
Springboot
Swagger/OpenApi
Azure Pipelines
Trivy Integration
Apache Sling
OSGI
Java Content Repository (JCR)
Apache Jackrabbit Oak
Adobe HTL
GraphQL
Maven
GitLab
IntelliJ
Azure Cloud
Azure DevOps
Terraform
AEM specialist in the Scrum team
Development and deployment of microservices via Open API interfaces
Operation of microservices in the Azure Cloud
Implementation of AEM modules and integration with microservices
Member of the knowledge transfer team and a backend coordination team
Sebastian Thees
Last position:
Software Engineer / Cloud Engineer at OC Fulfillment GmbH
- Hybrid role as the first software engineer in the company to bootstrap the organization, laying out technical foundation and advising management on organizational aspects.
- Set up the SaaS platform architecture, selected languages and tools, and designed processes to deliver customer value quickly and reliably.
- Designed and implemented build and continuous deployment pipeline with multi-tenant approach enabling extreme scaling of the SaaS platform.
- Established initial ITSM and support processes, provided monitoring and alarming, and participated in the on-call team.
- Proposed new approaches to scale the platform and improve backend interfaces to mitigate bugs and communication overhead.
- Mentored new employees and served as a trustful team member and lateral leader.
- Conducted interviews for technical roles.
- Used technologies: Typescript, Node.js, Bash, Google Cloud Platform (App Engine, Cloud Run, Cloud Functions, Google Endpoints, Firebase), GitHub Actions, Docker, Terraform, MongoDB, Firebase, REST APIs, GraphQL.
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
Andreas Beckers
Last position:
Senior Frontend Developer at Roadex
- Development of an app
- Technologies: React Native, Expo, SupaBase, TypeScript, GitHub, Trello
Alexander Jahn
Last position:
Freelancer at Bayer
- IoT development in Kotlin/Python.
Jacqueline Krech
Last position:
OTTO
- Design, development, and monitoring of microservices
- Migrating functions from a monolithic system into separate microservices
- Designing and implementing new microservices (backend and frontend)
- Setting up and maintaining a CI/CD pipeline (GitHub Actions)
- Configuring cloud infrastructure with AWS CDK and Terraform
- Designing and implementing event-driven communication with AWS SNS/SQS and Apache Kafka
- Ensuring code quality through Test Driven Development (TDD), static code analysis, and Clean Code
Discover over 15,000 top freelancers
Statistics of experts using Kotlin
Aggregated from the professional profiles of matched freelancers.
Experience
18 years (Germany: 17 years)
Position duration
2.2 years (Germany: 2.7 years)
Positions per freelancer
9 (Germany: 12)
Top business areas
Information Technology, Product Development, Quality Assurance
Top industries
Information Technology, Retail, Transportation
Certification focus areas
Information Technology, Product Development, Project Management
Bachelor's degree or higher
100% (Germany: 93%)
Master's degree or higher
75% (Germany: 57%)
Doctorate
13% (Germany: 10%)
Certifications per freelancer
2
Most common languages
German, English, French
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 Cologne 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 Cologne 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 in practice
Kotlin is a modern language for the JVM, Android, backend services, and shared code across platforms. Companies use it to build clean application logic, stable APIs, mobile features, and internal tools that need concise code and strong safety defaults.
Common delivery areas
- Android apps and app modules
- Backend services on Spring Boot or Ktor
- Shared logic with Kotlin Multiplatform
- Migration from Java codebases
- Test automation and build setup
Ecosystem and tooling
Strong Kotlin specialists work comfortably with Gradle, IntelliJ IDEA, Coroutines, Flow, and the JVM ecosystem. They also know when to use Java libraries, how to structure modules, and how to keep code readable for mixed teams that maintain long-lived products.
When companies bring help
Freelance Kotlin expertise is useful when a team needs to start a new service, rescue a legacy codebase, or speed up Android delivery. It also helps when a Cologne-based team wants short-term support for a local product squad while keeping collaboration partly remote and partly on-site.
What strong specialists show
A good Kotlin professional writes clear code, handles null safety well, and avoids unnecessary complexity. They understand concurrency, API design, testing, and build performance, and they can explain trade-offs between Kotlin-only solutions and mixed Kotlin and Java systems.
Search terms and fit
People often search for Kotlin, Kotlin JVM, KMP, or Kotlin Multiplatform when they need the same skill set. The best fit depends on whether the work is mobile, backend, or shared code, and on how much of the existing system already runs on the JVM.
Frequently asked questions
Before you brief your next project: the most common questions about Kotlin.
Kotlin is used for Android apps, backend services, shared business logic, and JVM-based internal tools. Many teams also use it for Kotlin Multiplatform when they want to reuse code across mobile or other client apps. It fits well when code clarity and safety matter more than raw volume of code.
Kotlin is usually chosen when a team wants less boilerplate, safer null handling, and smoother async code. Java still matters in many systems, especially where existing libraries and older services dominate. The right choice depends on the current codebase, the target platform, and how mixed the team is.
Kotlin Multiplatform makes sense when you want to share business logic, network layers, or validation rules across Android and iOS, or across mobile and backend. It is not the best answer for every app layer, so a strong specialist should assess where shared code really reduces effort. KMP is most useful when teams want reuse without forcing full UI sharing.
A strong Kotlin specialist usually knows the JVM ecosystem, Gradle, testing, and at least one server framework such as Spring Boot or Ktor. For mobile work, Android APIs, app architecture, and release flows matter as well. For shared code, experience with Kotlin Multiplatform and dependency management is important.
Kotlin work benefits from expert help as soon as a project has more than a simple proof of concept. Migration work, app architecture, concurrency, and module boundaries are places where small mistakes become expensive later. Bringing in a specialist early is often easier than cleaning up after a rushed start.
Yes, Kotlin work is often done remotely because code reviews, build checks, and issue tracking fit distributed collaboration well. Cologne teams may still want on-site time for planning, pairing, or release support, especially when the work touches several product owners. A good freelancer can adapt to both styles.
Look for clear module structure, good test coverage, and practical use of Coroutines, Flow, and null safety in Kotlin code. A strong specialist should explain why they chose a certain architecture and how they would keep it maintainable over time. Review past work for API design, build stability, and readable naming.
No. Kotlin is important on Android, but it is also widely used for backend services on the JVM and for Kotlin Multiplatform projects. Companies often hire for one of those areas first and later expand the scope once the codebase proves stable.
The average hourly rate of freelancers in Cologne, Germany who have used Kotlin in their recent projects is 93 €, which corresponds to a daily rate of about 744 € based on an 8-hour working day.
Of the freelancers in Cologne, Germany who have used Kotlin in their recent projects, 100% hold at least a Bachelor's degree, 75% hold at least a Master's degree, and 13% hold a doctorate.
On average, freelancers in Cologne, Germany who have used Kotlin in their recent projects have 18 years of professional experience, with a single engagement typically lasting around 2.2 years.
The most common languages among freelancers in Cologne, Germany who have used Kotlin in their recent projects are German (100%), English (100%), and French (18%).
The most common industries among freelancers in Cologne, Germany who have used Kotlin in their recent projects are Information Technology (91%), Retail (55%), and Transportation (45%).
The most common business areas among freelancers in Cologne, Germany who have used Kotlin in their recent projects are Information Technology (100%), Product Development (100%), and Quality Assurance (55%).
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 Dusseldorf Leipzig Dortmund Essen Bremen Dresden Hanover Nuremberg 
Berlin 
Hamburg 
Munich 
Frankfurt 
Dusseldorf Request a free demo
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Philipp Thomaschewski
FRATCH CEO
