Swagger Expert in Cologne
to make APIs clear, testable and ready to use with precise AI matchingHire experts who design OpenAPI specifications, generate client and server code, and publish interactive Swagger UI documentation. Get matched quickly with vetted, available freelancers who fit your API project and collaboration needs.
Meet FRATCH Experts in Cologne, who have recently used Swagger
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
Rainer L.
Last position:
Senior IT Consultant, Senior Software Architect, Senior Software Developer, Senior DevOps Engineer at Techniker Krankenkasse
Automation of the database major / minor releases for the TKeasy project
Concept for database major / minor release automation
As-is analysis
Evaluation of Redgate Flyway functionality
Concept creation
Products: Redgate Flyway, GitHub, Quest, Erwin Data Modeller, Oracle, Atlassian Jira, Atlassian Confluence
Skills: Docker, Continuous Delivery, Continuous Integration, Redgate Flyway, Major Releases, Minor Releases
Allal K.
Last position:
Java Senior Full Stack Developer at Insurance ÖRAG
- Further development of a policy administration system (contract/claims) for the legal expenses insurer ÖRAG.
- My role: Senior Software Developer.
- The team consists of 12 developers.
- Technologies used: Java 8/21, Java EE, Quarkus, WebLogic, JPA, RabbitMQ, JTA, CI, CD, Jenkins, DB2, Maven, Jenkins, GIT (bitbucket) later GitLab, Junit, Elasticsearch, Mockito, Jira, SonarQube, Scrum, React, Workflow
- Migration and modernization of legacy systems: rewrote C and C++ code in Java to improve maintainability, scalability, and performance. Refactored Python into Java, including optimization and integration into modern architectures.
- Study on the use of AI (Codex) for implementing a Java feature. The goal is to compare the time spent and productivity of AI-supported development with a classic implementation by a developer. The results should show how strongly the use of AI affects development time and efficiency.
- Development of the following tariff calculators for the years 2024/2026: private, companies, doctors, farmers, owner-occupied G + H, landlords, traffic, club, top managers, sales representatives, special criminal law, savings bank, municipal, BayGT, doctors, Dehoga
Alexander R.
Last position:
Business Analyst at Financial Services Provider Landesbank
The Helaba ATLAS project aims to modernize core systems and make them future-proof. As part of the subproject, the existing legacy system for international payments is being replaced by a modern web-based application.
- Analysis of functional and technical requirements
- Analysis and optimization of business processes
- Process modeling
- Preparation and facilitation of workshops
- Defining project scope and prioritizing requirements
- Business process management (analysis, modeling, and optimization)
- Specification of user stories
- Designing business and authorization concepts
- Testing and acceptance
- Designing mockups in Figma
- Creating the UI/UX style guide for web applications Approach: Scrum (agile) Technologies: Jira, Confluence, MS Teams, Conceptboard, Java, Vaadin, Figma
Jens H.
Last position:
#52 Test Manager in Safety-Critical Infrastructure at Telecommunications Company
- Network elements, network, operational and operator-related systems
- Supporting around 20 different products (managed agile)
- Requirements analysis and management (functional and non-functional)
- Test concept and planning (scope, test phases, effort, schedule, resources, organization, etc.)
- Aligning approach with clients and service providers
- Managing and assisting in creation of test cases for system, integration and end-to-end tests
- Guiding and supporting test execution
- Defect management and planning bug fixes with external providers
- Preparing and facilitating workshops
- Regular reporting and creating automated test reports
- Further development of agile testing methodology and configuration of supporting tools
- Conceptual support in developing a quality seal for rating product and service quality of internal and external providers
- Requirements engineering based on ISO/IEC 25010, Scrum, SaFE
- BMC Remedy, Atlassian Confluence, Atlassian Jira (including plugins Xray, Structure), Microsoft Office (incl. Visio), Obsidian, doxis document management system, Gitlab, Obsidian
Andreas K.
Last position:
Backend Developer at Univention GmbH
- Developed a SCIM-compliant Python interface to connect external systems
- Expanded and enhanced UCS modules in Python
- Extended and newly developed Helm charts for container orchestration in Kubernetes
- Maintained and further developed CI/CD pipelines in GitLab
- Implemented automated tests with Pytest and Playwright
'Nubus' is based on a microservice architecture, relies on open source technologies, and runs in Docker containers.
UCS is an IAM complete solution based on Debian, used as an alternative to Microsoft's Active Directory. The work was characterized by the close integration of infrastructure and application logic.
Predrag P.
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.
Vladimir M.
Last position:
Developer at Financial services provider
- Support and further development of a framework for developing applications in a banking association: DynS/OSPE
- Migration of the framework to Java 11 and Java 17
- Java8, Java11 and Java17, Spring, Spring-Batch, Spring WebServices, Spring-Security, Spring-Data, JPA, Hibernate, OpenSource libraries etc.
- XML, JAXB, JSON, REST and SOAP services, DB2, Oracle, WebSphere or Liberty AS, FreeMaker, Junit, mock libraries, JaCoCo, Maven, IntelliJ, Eclipse, GitHub, SVN, Jira
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
André F.
Last position:
GenAI Product Owner at OW Media Solutions GmbH
- Designed and led the development of an automated short-video generation system.
- Built a scalable AWS backend using Step Functions, Lambda, S3, ECS Fargate, and DynamoDB.
- Developed video rendering with OpenCV and FFMPEG; ensured maintainable Python code.
- Supervised and mentored a Python developer and trained the client in AI workflows.
- Decreased end-to-end production time from hours to minutes.
- Created a modular, extensible architecture designed to support future AI models.
Jyothikrishna S.
Last position:
Senior Back-end Engineer at RLE Engineering and Services GmbH
- Works at Ford Motor Company as Senior Back-end Developer on contract via outsourcing
- Designed and developed REST APIs based on the analyzed requirements and technical standards
- Investigated issues and defects to determine root causes and formulate corrective action measures
- Participated in QA, stage, and production release activities
- Conducted code reviews for performance improvement
- Provided monitoring and support using GCP
- Used test driven and behaviour driven development approaches
- Took part in agile ceremonies
Fatih K.
Last position:
Mobile App Developer at ING Belgium
- Part of a squad focused on intensive module development and integration
- Close collaboration with other squads and teams to integrate modules and essential components
- Use of SwiftUI and the Coordinator pattern to develop clean and understandable code
- Creative collaboration with UX designers in Figma and implementation in code
- Industry: Banking
- Project language: English
- Organizational form: Kanban
- Tools: Azure, Confluence, Figma, Teams
- Team size: 40 people
- Version control: Git, GitFlow, Azure
- App Store product: ING Banking
- Programming languages: SwiftUI, Swift
- Patterns: Coordinator, MVVM
- Swift Package Manager
- Localization: Yes
- Testing: XCTest, XCUITest
Andreas B.
Last position:
Senior Frontend Developer at Roadex
- Development of an app
- Technologies: React Native, Expo, SupaBase, TypeScript, GitHub, Trello
Discover over 15,000 top freelancers
Statistics of experts using Swagger
Aggregated from the professional profiles of matched freelancers.
Experience
19 years
Position duration
1.7 years
Positions per freelancer
15 (Germany: 14)
Top business areas
Information Technology, Product Development, Quality Assurance
Top industries
Information Technology, Banking and Finance, Government and Administration
Certification focus areas
Information Technology, Product Development, Project Management
Bachelor's degree or higher
100% (Germany: 90%)
Master's degree or higher
73% (Germany: 55%)
Doctorate
9% (Germany: 10%)
Certifications per freelancer
1 (Germany: 2)
Most common languages
German, English, French
Speak two or more languages
100% (Germany: 98%)
Based on our profile pool as of 19 Sep 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 Swagger
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 19 Sep 2026. Actual rates may vary depending on seniority level, experience, skill specialization, project complexity, and engagement length.
Swagger 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 (62%)
- Government and Administration (62%)
- Transportation (54%)
- Telecommunication (54%)
- Automotive (46%)
- Education (38%)
- Healthcare (38%)
Please note that freelancers can work across multiple industries, so percentages overlap.
About the technology
API documentation
Swagger is a set of tools for describing, documenting and testing HTTP APIs. It is closely associated with the OpenAPI Specification, which defines endpoints, parameters, authentication, request bodies and responses in a machine-readable format. Teams use it to create a shared contract between services, frontends and external consumers.
Core toolkit
The Swagger ecosystem supports the full API lifecycle:
- Write and validate OpenAPI definitions with Swagger Editor
- Present interactive reference documentation with Swagger UI
- Generate client libraries and server stubs with Swagger Codegen
- Explore endpoints and send test requests from a browser
Swagger tools work with YAML or JSON specifications and fit REST API workflows across many languages and frameworks. Strong specialists also understand schema design, reusable components, versioning and security schemes such as OAuth 2.0 and API keys.
Where it fits
Companies use Swagger for internal services, public APIs, partner integrations and microservice contracts. It helps teams align product, frontend and backend work before implementation and gives consumers a practical way to understand available operations. In Cologne, it can support distributed teams in logistics, manufacturing, media and software services without requiring every collaborator to work on site.
When to bring help
Freelance expertise is useful when an API has inconsistent documentation, unclear ownership or several consumers with different needs. Typical triggers include:
- Converting an existing REST API into a reliable OpenAPI contract
- Introducing contract-first development across services
- Automating documentation and validation in CI pipelines
- Preparing a public API for partners or external customers
A specialist can also review breaking changes, improve examples and connect the specification to API gateways, test suites or release processes.
Quality signals
Strong Swagger professionals treat the specification as part of the product, not as a document added after coding. They model resources consistently, describe error responses, set realistic examples and keep generated output under control. They know when to use reusable schemas, how to represent pagination and how to document edge cases without making the contract confusing.
Related skills
Useful adjacent knowledge includes REST design, HTTP semantics, JSON Schema, authentication, API testing and version control. Experience with tools such as Postman, Git, CI systems and gateway products helps turn an OpenAPI file into a dependable delivery workflow. Quality is visible when documentation matches live behavior, validation catches regressions and consumers can start quickly without informal explanations.
Frequently asked questions
What clients ask us most about Swagger — answered in short.
Swagger is used to describe REST APIs, generate interactive documentation and support testing from a defined contract. Its tools can also generate client libraries or server stubs from an OpenAPI document.
OpenAPI is the specification now maintained as an open standard, while Swagger is the family of tools that helped popularize it. Many people still say Swagger when they mean an OpenAPI definition or the surrounding tooling, including Swagger UI and Swagger Editor.
Swagger describes the API contract and can render documentation directly from it, whereas Postman is primarily used for sending requests, organizing collections and running tests. They often work together: the OpenAPI definition explains the interface, while Postman supports exploratory and automated testing.
Swagger work benefits from knowledge of REST design, HTTP status codes, JSON Schema and API security. A strong specialist may also work with OAuth 2.0, API gateways, Git, CI pipelines and testing tools such as Postman.
Swagger projects vary widely, so the right level depends on the API's scope and risk rather than a fixed timeline. For a small documentation cleanup, practical OpenAPI knowledge may be enough; a platform-wide contract-first rollout calls for experience with versioning, governance and automation.
Swagger work is well suited to remote collaboration because specifications, reviews and validation can be managed in shared repositories and CI systems. A Cologne company should clarify its preferred working language, overlap for workshops and whether occasional on-site API design sessions are needed.
Swagger quality is shown by accurate contracts, useful examples, consistent schemas and clear handling of errors and security. Ask the specialist to review a sample API or explain how they would detect drift between the specification and the running service.
Swagger is less suitable when an interface is not HTTP-based or when a team needs a different contract format for technologies such as GraphQL or event-driven messaging. It can still document surrounding REST endpoints, but the chosen tool should match the actual communication model.
The average hourly rate of freelancers in Cologne, Germany who have used Swagger in their recent projects is 94 €, which corresponds to a daily rate of about 753 € based on an 8-hour working day.
Of the freelancers in Cologne, Germany who have used Swagger in their recent projects, 100% hold at least a Bachelor's degree, 73% hold at least a Master's degree, and 9% hold a doctorate.
On average, freelancers in Cologne, Germany who have used Swagger in their recent projects have 19 years of professional experience, with a single engagement typically lasting around 1.7 years.
The most common languages among freelancers in Cologne, Germany who have used Swagger in their recent projects are German (100%), English (100%), and French (31%).
The most common industries among freelancers in Cologne, Germany who have used Swagger in their recent projects are Information Technology (100%), Banking and Finance (62%), and Government and Administration (62%).
The most common business areas among freelancers in Cologne, Germany who have used Swagger in their recent projects are Information Technology (100%), Product Development (92%), and Quality Assurance (77%).
Main locations of FRATCH Experts, who have recently used Swagger
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 Countries:
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FRATCH CEO
