Kotlin Experts in Cologne
matched in minutes from over 15,000 CVsHire experts who deliver Android applications, Kotlin backend services and multiplatform solutions with tools such as Jetpack Compose, Ktor and Coroutines. FRATCH matches you quickly and precisely with vetted, available freelancers.
Meet FRATCH Experts in Cologne, who have recently used Kotlin
Predrag P.
Last position:
Test Developer | Test Automation Engineer at CreditReform
Technologies: Java 25, Selenium, Insomnia, SSO, Gitlab, Jenkins, Docker, Kubernetes, Jira, IntelliJ, Nexus, Oracle, MariaDB, SpringBoot, Grafana, Concept Board, Vue.js, OpenApi, Kotlin. Implementation, maintenance, and enhancement of automated end-to-end regression tests for UI and API interfaces. Appropriate and targeted test automation involving multiple software products, including Java-based Windows applications. Automation of business processes with Selenium, reset jobs, and DB import jobs, as well as creation of test concepts, test case descriptions, and structured defect reporting.
Andreas B.
Last position:
Senior Software Developer at ELIONOVA AG
- Created an application to control measurement hardware with a Tauri application using React.JS and TypeScript on Raspberry Pi
- Developed a cloud application for storing and analyzing measurement results using Spring Boot and React.JS
- Built a Tauri application for printing ZPL labels on Windows
- Technologies: Java, JavaScript, Tauri, Rust, React.JS, AWS, Kubernetes, Docker, GitLab CI/CD, REST API (JSON), Maven, CI/CD, PostgreSQL
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
Ayhan G.
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 E.
Last position:
Consultant at Iteratec GmbH
Louis N.
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 T.
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 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
Thomas P.
Last position:
Freelance Software Architect at Self-employed
Alexander J.
Last position:
Freelancer at Bayer
- IoT development in Kotlin/Python.
Jacqueline K.
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
2.5 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: 55%)
Doctorate
13% (Germany: 9%)
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 29 Oct 2026.
Daily rate distribution
The chart shows how the daily rates of experts in this technology in Cologne 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 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 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 (91%)
- Retail (55%)
- Transportation (45%)
- Healthcare (36%)
- Banking and Finance (27%)
- Insurance (27%)
- Telecommunication (27%)
- Biotechnology (18%)
Please note that freelancers can work across multiple industries, so percentages overlap.
About the technology
Language and scope
Kotlin is a statically typed programming language created by JetBrains. It runs on the Java Virtual Machine, interoperates closely with Java and also targets Android, JavaScript and native platforms. Its concise syntax, null-safety features and support for functional and object-oriented patterns help teams build maintainable software.
What Kotlin builds
Kotlin is widely used for Android applications, backend services, shared mobile code and business software. It supports modern user interfaces, APIs, event-driven services and applications that need dependable integration with existing Java systems.
- Native Android applications with Jetpack Compose or XML layouts
- Backend APIs and services with Ktor or Spring Boot
- Shared logic with Kotlin Multiplatform
- Data, authentication and messaging integrations
Ecosystem and tooling
Strong Kotlin work includes more than language syntax. Professionals use Gradle, Android Studio, IntelliJ IDEA, Coroutines, Flow, serialization libraries and testing frameworks. They may also work with Java, SQL, REST, GraphQL, Docker and cloud deployment tools, depending on the product.
When expertise helps
Companies bring in freelance Kotlin specialists when a mobile product needs focused delivery, a Java codebase is being modernized or a backend team needs additional capacity. Cologne companies can combine local workshops with remote implementation, provided communication, documentation and delivery routines are clear.
- Establishing project structure, coding standards and build pipelines
- Migrating Java or legacy Android code to Kotlin
- Improving app performance, stability and test coverage
- Sharing domain logic across mobile platforms
What strong specialists deliver
Experienced professionals choose Kotlin features for clarity rather than novelty. They define clear module boundaries, handle Coroutines and cancellation safely, model nullable data carefully and keep APIs easy to test. They also understand release workflows, observability and the operational needs behind production software.
Selecting the right fit
Review work that resembles your system: Android UI, Ktor services, Spring Boot integration or Kotlin Multiplatform, as relevant. Ask how the specialist approaches architecture, testing, dependency upgrades and Java interoperability. For Cologne-based collaboration, confirm availability for on-site sessions if needed and agree on the language used for technical work.
Frequently asked questions
Before you brief your next project: the most common questions about Kotlin.
Kotlin is used for Android apps, backend services, shared mobile logic and software that runs alongside Java systems. It is also suitable for command-line tools, web services and applications targeting multiple platforms.
A strong Kotlin specialist can use the existing Java ecosystem while writing more concise code with built-in null-safety and modern language features. Java may still be a practical choice when a team has deep Java expertise or depends on Java-specific tooling, so the decision should reflect the codebase and delivery goals.
A capable Kotlin professional may also work with Android Studio, Gradle, Jetpack Compose, Coroutines, Ktor, Spring Boot, SQL and REST APIs. The right combination depends on whether the assignment focuses on mobile apps, backend systems or shared Kotlin Multiplatform code.
The required depth depends on the system and its risks. A small Android feature may need focused Kotlin delivery, while a migration, shared mobile architecture or high-traffic backend calls for a specialist who has handled testing, releases, performance and Java interoperability in production.
Yes. Kotlin work is well suited to remote collaboration through version control, code review, issue tracking and automated builds. Cologne teams should define meeting rhythms, documentation standards and any need for on-site workshops before the engagement begins.
Kotlin Multiplatform can be useful when mobile products should share domain logic, networking or data access while retaining platform-specific user interfaces. A specialist should first assess the existing apps, team skills and required native integrations rather than assuming that all code should be shared.
Review how the Kotlin specialist explains architecture, error handling, testing and dependency choices. Practical evidence includes readable modules, safe Coroutine usage, reliable build automation, useful tests and clear handling of interoperability with Java or platform APIs.
A Kotlin freelancer may work on Android features, backend APIs, Java modernization or cross-platform modules. Assignments often include technical discovery, integration with existing services, code reviews, automated testing and support through release or handover.
The average hourly rate of freelancers in Cologne, Germany who have used Kotlin in their recent projects is 88 €, which corresponds to a daily rate of about 707 € 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 2.5 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 
Frankfurt 
Stuttgart 
Dusseldorf 
Dortmund Countries:
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