Kotlin Experts in Berlin
matched in minutes from over 15,000 CVsHire experts who deliver Android applications, Kotlin/JVM backend services and Kotlin Multiplatform solutions. FRATCH connects you with vetted, available freelancers through fast, precise AI matching.
Meet FRATCH Experts in Berlin, who have recently used Kotlin
Toralf C.
Last position:
IT Consultant in PKI Software Development at BWI
- Implementation of a full-stack application with Angular as frontend framework and Java as backend language
- Use of the Swagger OpenAPI specification for REST communication between frontend and backend applications
- Control of a card printer via the Nexus Card SDK framework
- Design and implementation of card management software with web interface and JavaFX module for printer monitoring
- Use of Cucumber tests for test automation and creation of test artifacts for testing outside the development environment
- Use of Wireshark for network investigations to analyze the API of a third-party product and to check the REST API of the self-developed software
Imran A.
Last position:
Software Engineer II at LivePerson Germany GmbH
- Led development of 15+ microservices (Java 17, Spring Boot) driving customer interactions; migrated from on-prem to GCP Kubernetes, improving scalability and reducing infra cost by 20%.
- Optimized user services with CouchDB caching and API refactoring, cutting response times by 35% and enhancing customer experience.
- Implemented canary deployments, FluxCD GitOps, and CI/CD optimizations in GitLab, reducing release lead time by 25% and enabling zero-downtime rollouts.
- Set up Grafana health checks and Anodot alerts for latency, error, and throughput monitoring, reducing MTTR by 40%.
- Built secure APIs using OAuth2, DPoP, and Gatekeeper, integrated REST and GraphQL, and achieved 90%+ test coverage with unit and E2E tests.
- Mentored junior developers, promoted Agile best practices, and collaborated cross-functionally to deliver high-impact, reliable customer-facing features.
Viktor S.
Last position:
AI Engineer (Freelance) at Empion
Enterprise AI content categorization and AI-powered web research.
- Built multi-LLM evaluation framework with annotated data
- Iterated LLM error rates based on annotated datasets
- Implemented AI-powered web research pipeline Stack: LLM, evals, OpenRouter, Python, Node.js, TypeScript, React
Rüdiger S.
Last position:
Full-Stack Software Engineer / Consultant for Digitalization at ARTEVENT
Designed, built, and launched an internal event planning web application used by over 100 department leads for a large event, despite having no dedicated testing phase.
Ensured smooth, failure-free operation during first production use, leading to the tool being adopted for future events.
Automated catering calculations and related workflows, significantly reducing email communication and manual computation effort for meal planning.
Managed deployment and hosting on a Linux server using Coolify, including application setup and runtime operations.
Hired and guided a communication designer on UX while independently owning all technical decisions and implementation.
Marvin M.
Last position:
Co-founder & CTO · Freelance Software Engineer (AI & SaaS) at Self-employed
- Self-employed · Berlin, Germany
- Co-founded the company and own the entire technical side: product architecture, backend, frontend, infrastructure and operations.
- Designed and built the Automated Booking System (ABS) as well as the core platform and payment logic.
- Development of AI-powered SaaS products, from architecture through backend and frontend to production operation.
- Technical consulting on product architecture, data protection and permissible automation.
- Building, running and monetising my own API products for AI agents, each available as a REST interface and as an MCP server.
- Full ownership of architecture, infrastructure, billing, legal texts and go-to-market.
Abhiroop B.
Last position:
Software Engineer III at Foundry Digital
- Developed and deployed microservices in Kotlin and Spring Boot, integrated AWS Secrets Manager to secure credentials and decreased network calls using Spring cache.
- Refactored Kafka consumer using Spring Kafka with semaphore-based backpressure to cap records and keep heap memory stable under spikes; switched to batch upserts to cut down on database invocations; added Testcontainers integration tests for Kafka and database to pave the way for future changes.
- Automated the financial reconciliation workflow in Spring Boot (Kotlin) using Spring Scheduler, transactional boundaries, JPA/Hibernate on MySQL, and Flyway migrations, saving the accounts team 16+ hours per week.
- Designed and dockerized payments end-to-end test framework in Robot (Python) with reusable keyword libraries and profiles; integrated with GitLab CI (JaCoCo XML and HTML reports) to accelerate releases and lift code coverage to 80%.
- Implemented end-to-end observability on Datadog by instrumenting services with Datadog APM, correlating metrics and logs, provisioning dashboards, and creating monitors with burn-rate alerts and anomalies to harden reliability and give stakeholders clear visibility.
Santhosh K.
Last position:
Freelance Software Engineer at Zalando SE
- Drive migration of enterprise authorization platform from Styra DAS to open-source OPA via Skipper (Zalando's Golang-based ingress proxy) integration
- Optimise k8s resources and integrate native Prometheus metrics with OPA
- Migrate from internal monitoring solution to Prometheus CRs + Dash0
Tech Stack: Java/Kotlin, Golang, Python, Spring Boot, AWS, Kubernetes, Docker, OpenTofu, Prometheus, Grafana
Cristian P.
Last position:
iOS Team Lead at Qlaunch Gmbh
- Contributed to the architecture design process, resulting in scalable and maintainable solutions for complex projects.
- Enhanced app performance by optimizing code and implementing efficient algorithms.
- Stayed current with industry trends to ensure implementation of best practices in app development.
- Led a team of iOS developers for timely completion of projects and achieving client satisfaction.
- Translated basic design plans into full iOS app frameworks, delegating project components to appropriate team members.
- Estimated work hours and tracked progress using Scrum methodology.
Matthias Z.
Last position:
Senior Flutter Developer at Materna
- Developed a Flutter app for eID ID card logins
- Focus: Flutter, iOS, eID, AusweisAppSDK, Mason, Keycloak, Agentic Coding, Arc42, Jenkins
Maciej R.
Last position:
Full Stack Developer (Freelancer) at Runbuggy
- Led development of RunBot AI assistant autonomously using LLM-powered workflow automation (React, TypeScript, Java, MongoDB, NATS)
- Architected TMS platform providing unified transportation management and real-time logistics visibility with AI processing pipelines
- Designed event-driven microservices architecture supporting marketplace
- Drove architectural decisions and technical leadership across full-stack platform development
Mathias V.
Last position:
Fullstack AI Engineer at Ammodia.com
Developed a custom Kotlin Multiplatform app with a Spring backend and AI features.
Ben S.
Last position:
AI Trainer & Data Annotator at Scale AI
- RLHF & Model Evaluation: Evaluated, ranked, and refined Large Language Model (LLM) responses based on accuracy, reasoning quality, safety guidelines, and factual correctness.
- Data Annotation & Prompt Engineering: Created high-complexity prompts, edge-case scenarios, and gold-standard reference answers to train and fine-tune generative AI models.
- Quality Assurance & Verification: Conducted rigorous fact-checking, logical consistency validation, and multi-turn response optimization.
Mohsin H.
Last position:
BBM GenAI MiDAS program coordinator for Bosch eBike at Robert Bosch GmbH
The MiDAS program aims to integrate Generative AI across the entire BBM organization. My role is to enable the eBike division to adopt and leverage Generative AI by collaborating closely with the MiDAS team in India.
Management:
- Enable the eBike division to adopt GenAI through tailored solutions.
- Collaborate with the MiDAS team in India to design solutions for Generative AI use cases specific to the eBike division.
- Coordinate with the eBike teams to integrate GenAI systems, tools, plugins, and services provided by the MiDAS team.
- Plan roadmaps with eBike and MiDAS India team Product Managers for the delivery and integration of Generative AI solutions.
Can K.
Last position:
DevOps Specialist at Eviden Germany GmbH
Manage the development release and update process for a digitized nationwide trade register project "AuRegis".
Support software in Kubernetes/OpenShift environments, configure management with Kustomize, and implement CI/CD pipelines using Jenkins/GitLab, SonarQube, ArgoCD, and Azure.
Oversee system release of microservice architecture.
Build the CI/CD stack from scratch with GitLab CI, integrating integration tests, dependency checks, and security measures.
Automate deployment onto OpenShift using Kustomize.
Set up infrastructure components for development, code review, and code quality analysis including SonarQube.
Integrate GitOps tools such as Kustomize and ArgoCD, using both Azure and private cloud for sensitive data handling.
Develop Python scripts in Jenkins for cryptostore configuration and system packaging of products and microservices into deployable units.
Automate delivery to customers and deployment on test systems.
Create Kustomize manifests for microservices and develop the related automation, treating documentation as code for clarity and reproducibility.
Serve as technical advisor for the project's first go-live and oversee further deployments as technical rollout manager.
Ibrahim H.
Last position:
Senior Full Stack / AI Engineer at Punktum Digital GmbH
- Context: Healthcare and laboratory teams required faster document analysis, treatment-planning support, and reliable AI workflows for MR/VR-assisted operations.
- Contribution: Built the AI healthcare platform, model/agent workflows, VR-glasses deployment platform, REST APIs, Next.js/React interfaces, and CI/CD pipelines.
- Impact: Delivered a production-ready AI product foundation that improved clinical document review, supported laboratory automation, and made VR fleet deployment manageable across environments.
Tech: TypeScript, Next.js, Node.js, React, Java, Spring Boot, Python, PyTorch, TensorFlow, Docker, PostgreSQL, OpenAPI, GitLab, GitHub Actions.
Discover over 15,000 top freelancers
Statistics of experts using Kotlin
Aggregated from the professional profiles of matched freelancers.
Experience
17 years
Position duration
2.2 years (Germany: 2.7 years)
Positions per freelancer
11 (Germany: 12)
Top business areas
Information Technology, Product Development, Project Management
Top industries
Information Technology, Retail, Media and Entertainment
Certification focus areas
Information Technology, Product Development, Project Management
Bachelor's degree or higher
95% (Germany: 93%)
Master's degree or higher
54% (Germany: 55%)
Doctorate
8% (Germany: 9%)
Certifications per freelancer
1 (Germany: 2)
Most common languages
English, German, French
Speak two or more languages
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 Berlin 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 Berlin 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 (96%)
- Retail (44%)
- Media and Entertainment (40%)
- Healthcare (38%)
- Automotive (36%)
- Banking and Finance (33%)
- Education (29%)
- Transportation (27%)
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 that runs on the Java Virtual Machine and interoperates closely with Java. Companies use it for Android applications, backend services, APIs, command-line tools and shared code across mobile and web systems. Its concise syntax, null-safety features and coroutine support help teams build maintainable software.
Android and mobile
Kotlin is the primary language for modern Android work. Professionals use it with Android Studio, Jetpack Compose, Android Jetpack libraries and Kotlin Coroutines to create user interfaces, background processing and device integrations. Kotlin Multiplatform can share business logic between Android and iOS while keeping native user experiences.
- Android applications with Jetpack Compose
- Kotlin Multiplatform mobile modules
- Offline data, notifications and device APIs
- Shared testing and mobile release workflows
Backend ecosystem
On the server, Kotlin/JVM fits established Java environments and enterprise delivery processes. Its ecosystem includes Spring Boot, Ktor, Micronaut, Gradle, Exposed and popular Java libraries. Kotlin services commonly expose REST or GraphQL APIs, process events, connect to SQL or NoSQL stores and run in containerized cloud environments.
When specialists help
Companies bring in freelance Kotlin specialists when an Android product needs a stable release path, a Java service is being modernized or a new backend requires strong type safety. Berlin teams may also need professionals who can collaborate on site, remotely or across distributed product groups, with clear English and, where useful, German communication.
- Migrating Java codebases to Kotlin
- Establishing coroutine and testing patterns
- Introducing Kotlin Multiplatform
- Improving application performance and reliability
Skills that matter
Strong professionals understand Kotlin beyond its syntax. They can assess Java interoperability, choose suitable coroutine scopes, structure modules and design APIs that remain easy to test. They also work confidently with version control, automated delivery, observability, security practices and the product constraints of mobile or backend systems.
Choosing the right expert
Review shipped Kotlin work that resembles your system, not only isolated code samples. Ask how the professional handles nullability, concurrency, dependency boundaries and migration risk. For Android, discuss Compose, lifecycle behavior and release operations; for backend work, examine API design, database access, resilience and cloud deployment. A good specialist explains trade-offs clearly and leaves behind tested, documented code.
Frequently asked questions
Key details about Kotlin, drawn from the questions we get asked most.
Kotlin is used for Android applications, backend services, APIs, desktop tools and shared mobile code through Kotlin Multiplatform. It is also common in Java-based enterprise systems where teams want concise syntax, null safety and modern concurrency features.
Kotlin runs on the JVM and works directly with Java libraries, so teams can adopt it without replacing an existing Java ecosystem. It usually requires less boilerplate and offers built-in null-safety features, while Java may remain preferable where a team depends on long-established conventions or specialized tooling.
Kotlin specialists often bring Android Studio, Jetpack Compose, Kotlin Coroutines, Gradle and automated testing experience. Backend projects may also require Spring Boot or Ktor, SQL, REST or GraphQL APIs, containers, cloud services and observability.
Kotlin project needs depend on risk, scope and the existing codebase rather than a fixed tenure threshold. A smaller feature may suit a professional who has delivered similar components, while a migration, shared mobile architecture or high-volume backend benefits from someone who has handled those decisions in production.
Kotlin work is well suited to remote collaboration because code review, automated tests and delivery pipelines provide clear shared workflows. For Berlin teams, agree early on overlap hours, documentation standards and whether English, German or both are needed for product and stakeholder communication.
Kotlin Multiplatform is useful when Android and iOS products should share domain logic, networking, validation or data access while retaining native interfaces. It is less suitable when the products have very different behavior or when the team cannot support the additional shared-module architecture.
Kotlin quality is visible in readable module boundaries, deliberate nullability, well-scoped coroutines and tests that cover behavior rather than implementation details. Ask a freelancer to explain trade-offs in a code review and inspect how the work handles errors, cancellation, Java interoperability and long-term maintenance.
Kotlin professionals should confirm the target platforms, language and library versions, build setup, delivery pipeline and boundaries with existing Java or native code. They should also clarify ownership of architecture decisions, testing expectations, release responsibilities and the definition of a finished deliverable.
The average hourly rate of freelancers in Berlin, Germany who have used Kotlin in their recent projects is 98 €, which corresponds to a daily rate of about 785 € based on an 8-hour working day.
Of the freelancers in Berlin, Germany who have used Kotlin in their recent projects, 95% hold at least a Bachelor's degree, 54% hold at least a Master's degree, and 8% hold a doctorate.
On average, freelancers in Berlin, Germany who have used Kotlin in their recent projects have 17 years of professional experience, with a single engagement typically lasting around 2.2 years.
The most common languages among freelancers in Berlin, Germany who have used Kotlin in their recent projects are English (98%), German (96%), and French (13%).
The most common industries among freelancers in Berlin, Germany who have used Kotlin in their recent projects are Information Technology (96%), Retail (44%), and Media and Entertainment (40%).
The most common business areas among freelancers in Berlin, Germany who have used Kotlin in their recent projects are Information Technology (98%), Product Development (93%), and Project Management (53%).
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.
Hamburg 
Munich 
Cologne 
Frankfurt 
Stuttgart 
Dusseldorf 
Dortmund Request a free demo
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