OpenAPI Experts in Frankfurt
matched in minutes with vetted, available freelancersHire experts who design API contracts, generate documentation and connect OpenAPI specifications with tools such as Swagger UI, Redoc and code generators. FRATCH uses precise AI matching to help you work with vetted, available freelancers quickly.
Meet FRATCH Experts in Frankfurt, who have recently used OpenAPI
Boian V.
Last position:
Solution Architect at DB InfraGO AG
The Base Services of DB InfraGO form a central data hub between the company’s IT systems. Common Data Services are developed that distribute data from source systems to a variety of downstream systems (via JMS) and make them available (via REST API). The existing service landscape based on TIBCO is being migrated to DB InfraGO’s cloud-native platform.
- Architecture design and implementation for performance-optimized bulk data processing of several million datasets at specific times during the day
- Technical specification and documentation of business requirements
- Integration of various subsystems (including SAP and Salesforce) through the reimplementation of more than 40 microservices based on Spring Boot
- Migration of TIBCO Based microservices from the Enterprise Integration Platform to the Cloud Native Platform using Spring-Boot
- Establishment of a deployment pipeline using GitLab CI/CD, Artifactory, and automated deployment to a Kubernetes environment with the help of ArgoCD
- Definition and implementation of automated unit, integration, and regression tests
Team Size: 9
Technologies/Tools: Java, Spring Boot, ActiveMQ(JMS), JUnit, Tibco Business Works, Gitlab (CI/CD), Kubernetes (Amazon AWS), ArgoCD, postgreSQL, Oracle, Postman, Hoppscotch, openAPI, Sonarqube
Waseem S.
Last position:
Solution Architect / Subject Matter Expert at FRMCS terminal device manufacturer
Participation in the EU-funded MORANE-2 project to validate the Future Railway Mobile Communication System (FRMCS) in real-life use cases: creation of the requirement specifications for TOBA as well as the associated test specifications.
Technologies: 5GS (Radio & Core), FRMCS, MCx (MCPTT, MCData, MCVideo), MC Gateway UE, MCx Priority/Security/QoS Management, ETCS, SIP, IMS
Michael H.
Last position:
Frontend Developer at RTL Tech
- Development and optimization of the RTL+ frontend application for SmartTV and set-top box platforms with React and Next.js.
- Key role in the technical coordination of developers within the team and in coordinating implementation.
- Central interface to adjacent teams to simplify development processes and improve cross-team alignment.
- Improved frontend performance, stability, and rendering behavior on low-powered devices in a restricted runtime environment.
- Implemented a frontend testing strategy with Jest, React Testing Library, and Playwright.
- Implemented accessibility improvements according to WCAG 2.2 and WAI-ARIA.
- Integrated Didomi Consent Management as a contribution to increasing ad monetization on streaming platforms.
- Used AI-supported engineering workflows with Cursor for structured implementation, refactoring, and faster problem solving.
Technologies used: React, Next.js, TypeScript, JavaScript, GraphQL, Apollo Gateway, Zustand, Tailwind CSS, Styled Components, React Testing Library, Playwright, Jest, HTML5, CSS3, AWS Lambda, EC2, CloudFront, S3, GitLab CI/CD, NX, Cursor
Saqib J.
Last position:
AI Developer / AI Engineer (Lead) at KOM4TEC GmbH
- Conceptual design and implementation of modular AI assistants for sales and business processes in the Microsoft ecosystem (Agentic AI, Copilot extensions)
- Frontend architecture and development with React + TypeScript for embedded chat and assistant surfaces (streaming UI, hooks, React Query, OpenAPI clients)
- Enterprise-level agent development: reusable skill/agent library, MCP server, review and compliance gates
- LLM integration into the user experience: Anthropic (Claude), OpenAI, tool use, RAG pipelines, prompt engineering, guardrails
- Architecture and code review consulting as well as mentoring in the AI development team
- Integration with Microsoft Graph, Power Platform, and Azure services
- Technologies: React, TypeScript, Anthropic Claude, OpenAI, MCP, RAG, Microsoft Graph, Power Platform, Azure
Uday V.
Last position:
Senior Full Stack Java Developer & DevOps Engineer at Deutsche Börse (DBAG)
Project: SCS (Settlement / Clearing Services)
Settlement platform serving multiple trading and clearing venues — counterparty risk safeguarding, settlement volume reduction, central risk management, and post-trade anonymity.
Technologies: Java 17, Spring Boot 3, Microservices, Spring Data JPA, SonarQube, Fortify (SCST), Mockito, Jenkins, OpenShift, Maven, Podman, GitHub, JIRA, Liquibase, Swagger, AMQP, Apache Camel, Terraform, PostgreSQL, Instana, Graylog.
- Identified and remediated CVEs in third-party libraries using SCA tooling, strengthening the security posture of production components.
- Maintained 90% code coverage with SonarQube, improving code quality and reducing production defects.
- Enabled mTLS for database authentication and message broker connections, enforcing encrypted, certificate-validated communication.
- Designed and deployed microservices with asynchronous, REST-based communication between components.
- Optimized a high-volume REST API (~200K requests) by reducing response time from 3s to 2s (33% improvement), boosting throughput and reliability under production load.
- Automated build and continuous integration pipelines using Maven and Jenkins.
- Orchestrated containerized workloads on Podman/OpenShift and governed schema evolution with Liquibase, ensuring reliable, repeatable deployments across all environments.
- Optimized Java code and implemented EHCache-based caching, improving application performance.
- Streamlined release management by governing application images, JAR versions, and dependencies through DBAG Artifactory, ensuring version consistency and audit traceability across environments
Ingo D.
Last position:
Analytics at BaFin - Federal Financial Supervisory Authority Frankfurt
- Introduction of methods for developing and automated deployment of cloud-native software and machine learning applications in OpenShift clusters
- Development of various programs in Python
- Technologies: Kubernetes, OpenShift, Kustomize, ArgoCD, Tekton, Docker, PodMan, Airflow, IntelliJ, PyCharm, Git, Bitbucket, Jira, Confluence, Python
Werner K.
Last position:
Test Coordinator, Designer and Engineer at IBM
- Testing the SekIDP and related components
- Test design, execution and automation, microservices, GitHub Enterprise, Eclipse, Katalon Test Platform, API Testing, Confluence 8, JIRA/Xray, Draw.io, Swagger/OpenAPI, Postman, Docker, Kubernetes, Podman, PuTTY, E-Health, Telematik, Gematik standards, EPA, E-Rezept, sektoraler IDP, encryption, XaDES, PaDES, DICOM, HL7, FHIR, IHE, ICD, SSO, SAML/Shibboleth, OAuth, smartcards, JWT, two factor authentication Android and iOS, Wireshark, BrowserStack, Cypress, gRPC, REST, SOAP, WS-Security, Linux Shell, PowerShell, SSH/SSL, Java, Kotlin, Cordova, Gradle, Groovy, Python, TypeScript
Jonas W.
Last position:
Fullstack Developer at Soulven Agency
- Working for customer and internal projects ranging from B2C, B2B applications
- Development and maintenance of customer-facing and internal applications across B2C and B2B domains
- Responsibility for technical direction, architectural decisions and code quality standards
- Design and implementation of scalable application architectures, including modular frontend and service-oriented backend structures
- Conceptual planning and technical execution of the agency website relaunch in Angular
- Rapid prototyping and MVP development for B2B customer projects in the pharmaceutical sector with Vue.js
- Creation of first MVPs for 3D rendering–based products, including real-time visualization and interactive experiences
- Strong UX/UI expertise with a focus on gamification, user engagement and conversion-driven interfaces
- Close collaboration with product management, design and stakeholders to translate business requirements into technical solutions
- Agile software development using Scrum, including sprint planning, reviews and retrospectives, supported by Azure DevOps
- Full-stack development using React, Angular, TypeScript, Vue.js, HTML5, CSS3/SCSS, C#, .NET, Node.js, RESTful APIs, Unity, Azure DevOps, Git and CI/CD pipelines
Timur Y.
Last position:
Lead Frontend Developer | Fullstack Developer at Finanz Informatik
- Further development of an application for managing personnel changes.
- Development of frontend and backend.
- Implementation of the frontend with React and Material UI.
- Implementation of the backend with Java and Spring Boot.
- Use of React, Java, Spring, TypeScript, next.js, Material UI, Github Enterprise, Figma, Docker, Playwright, swagger, swagger UI, OpenAPI, npm, yarn, git.
Felix T.
Last position:
Quality and Process Manager Trading – Systems Focus at Mainova AG
- Ensuring stable operation of business-critical applications in the energy environment (KRITIS-adjacent systems), coordinating with IT operations on certificates, permissions, and security-relevant logging
- Continuous monitoring of interfaces, processes, and system states including analysis of deviations and performance issues
- Development and setup of secure interfaces including authentication and access concepts
- Incident management: prioritization, root cause analysis, coordination of issue resolution with IT operations, business units, and external service providers
- Change and release management including coordination, test coordination, go-live, and post-live support
- Product owner for operational systems in day-to-day operations (forecasts, schedule management, market data import and export, contract management, regulatory reporting)
- Documentation of operational processes, changes, and incidents to ensure traceability and auditability
- Automation and digitization of operational processes
- Introduction and use of AI-supported analysis and monitoring approaches and agents with Microsoft 365 Copilot
Ralitsa P.
Last position:
Process, Project and Requirements Manager, Client Project @ RUBINLAKE at 1&1 Versatel GmbH
- Introduction of a new workflow tool for fibre connectivity & broadband delivery
- Requirements design, estimation and prioritization
- Creation of rollout and project plans
- Managing the development team using Scrum
- Design and project management of the API interface to existing tools
- Process modeling for the new order dispatching teams (FCD & BD)
- Designing processes inside and outside the team
- Requirements design and implementation of necessary tools
- Creation and calculation of production KPIs
Igor P.
Last position:
Senior Frontend Developer at Objego GmbH
Within the project, Objego's digital platform for real estate management was further developed.
Further development of various software modules within the application.
Continuous improvement and optimization of existing functionalities to enhance performance and user experience.
Design and implementation of unit tests to ensure code quality and stability.
Close collaboration with the QA team to quickly fix bugs.
Implementation of new features in coordination with stakeholders and end users.
Active member of the Scrum team with a focus on agile methods and continuous improvement of the software.
Technologies: Angular 16/17, Material, Angular CDK, Angular Elements, Nx, NgRx, NgNeat, NgX-Translate, NgX-Charts, NgX-Lottie, NgX-Markdown, Sentry, Azure AI Form Recognizer, Lodash, Dayjs, Flatpickr, Lottie-Web, Mixpanel, RxJS, Prettier, ESLint, Webpack, Cypress, Playwright, Jest, Husky, TypeScript, Node.js, Zone.js, Docker, Spring Boot, Git, Figma, Figma Token, Storybook, Jira, Confluence, Atlassian, Gitlab CI/CD, Codecov, Custom Design System, Mockoon.
Discover over 15,000 top freelancers
Statistics of experts using OpenAPI
Aggregated from the professional profiles of matched freelancers.
Experience
18 years (Germany: 19 years)
Position duration
2.3 years (Germany: 1.8 years)
Positions per freelancer
14
Top business areas
Information Technology, Product Development, Project Management
Top industries
Information Technology, Banking and Finance, Telecommunication
Certification focus areas
Information Technology, Project Management, Operations
Bachelor's degree or higher
89%
Master's degree or higher
44% (Germany: 50%)
Certifications per freelancer
2
Most common languages
German, English, Russian
Speak two or more languages
100% (Germany: 93%)
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 Frankfurt 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 Frankfurt using OpenAPI
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.
OpenAPI 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 (92%)
- Banking and Finance (58%)
- Telecommunication (58%)
- Healthcare (50%)
- Transportation (50%)
- Automotive (42%)
- Manufacturing (42%)
- Education (33%)
Please note that freelancers can work across multiple industries, so percentages overlap.
About the technology
API contracts
OpenAPI is a language-independent specification for describing HTTP APIs. It defines endpoints, parameters, request bodies, authentication, responses and data models in a structured document, usually written in YAML or JSON. Teams use that contract to align backend, frontend, mobile and external integrations before implementation.
Where it fits
OpenAPI specifications support REST APIs across internal services, public products and partner integrations. They can describe services built with Java, Spring Boot, .NET, Node.js, Python, Go or other web technologies. Common project goals include:
- Defining a consistent API contract across teams
- Publishing interactive documentation with Swagger UI or Redoc
- Generating client libraries, server stubs and test assets
- Validating requests and responses in delivery pipelines
Ecosystem and tooling
The wider ecosystem includes Swagger Editor, Swagger UI, Redoc, OpenAPI Generator and command-line validation tools. Strong specialists understand OpenAPI 3.x, reusable components, schema composition, security schemes and vendor extensions. They also connect specifications with API gateways, contract testing, CI/CD workflows and developer portals.
When expertise matters
Companies often bring in freelance expertise when an API has grown inconsistent, documentation no longer matches production or several teams need a shared contract. A specialist can assess existing endpoints, model a maintainable specification and introduce review rules without disrupting active releases. In Frankfurt, this work may combine remote delivery with on-site workshops for product and engineering teams.
Signs you need support
Look for outside expertise when API changes cause repeated integration issues or when consumers cannot understand authentication and error responses. A focused engagement can establish ownership and improve the path from design to release.
- Specifications differ between services
- Generated clients fail against live endpoints
- Documentation is maintained separately from code
- API reviews lack clear governance
What strong professionals deliver
The best OpenAPI professionals treat the specification as a living product contract, not as documentation added at the end. They use clear resource models, stable naming, precise response semantics and practical examples. They verify the contract against real services, explain trade-offs to technical and non-technical stakeholders, and leave teams with review patterns they can maintain. German and English communication can both matter when local teams and international consumers collaborate.
Frequently asked questions
Before you brief your next project: the most common questions about OpenAPI.
OpenAPI is used to describe HTTP APIs in a machine-readable contract. Companies use it to align teams, publish interactive documentation, validate implementations and generate client libraries or server scaffolding.
OpenAPI describes APIs that commonly use HTTP and REST-style resources, while GraphQL uses a query schema and gRPC relies on protocol buffers with remote procedure calls. The right choice depends on client flexibility, transport needs, tooling and compatibility with existing systems.
A strong OpenAPI specialist should understand REST design, HTTP semantics, JSON Schema, authentication methods and API versioning. Experience with Swagger UI, Redoc, OpenAPI Generator, contract testing and CI/CD integration is also useful.
The scope of the OpenAPI work matters more than a fixed tenure requirement. A small specification review may need focused specialist support, while a large service landscape requires proven experience with reusable schemas, governance, migrations and production validation.
OpenAPI projects are often suitable for remote collaboration because specifications, reviews and validation run through shared repositories and delivery pipelines. Frankfurt-based companies may still prefer on-site workshops for domain discovery, API governance or coordination across German- and English-speaking teams.
Review whether the OpenAPI document matches live behavior and clearly defines requests, responses, errors, security and reusable models. Good quality also shows in understandable examples, stable naming, successful validation and documentation that helps consumers act without guesswork.
Swagger is the former name associated with the specification and remains the name of a widely used tooling ecosystem. OpenAPI is the current specification name, while products such as Swagger UI and Swagger Editor continue to support authoring and presenting API definitions.
Working with OpenAPI often involves translating business behavior into precise API contracts and resolving differences between documentation and implementation. Specialists may also review pull requests, support generated artifacts, improve governance and coordinate with product, security and service teams.
The average hourly rate of freelancers in Frankfurt, Germany who have used OpenAPI in their recent projects is 100 €, which corresponds to a daily rate of about 796 € based on an 8-hour working day.
Of the freelancers in Frankfurt, Germany who have used OpenAPI in their recent projects, 89% hold at least a Bachelor's degree and 44% hold at least a Master's degree.
On average, freelancers in Frankfurt, Germany who have used OpenAPI in their recent projects have 18 years of professional experience, with a single engagement typically lasting around 2.3 years.
The most common languages among freelancers in Frankfurt, Germany who have used OpenAPI in their recent projects are German (100%), English (100%), and Russian (17%).
The most common industries among freelancers in Frankfurt, Germany who have used OpenAPI in their recent projects are Information Technology (92%), Banking and Finance (58%), and Telecommunication (58%).
The most common business areas among freelancers in Frankfurt, Germany who have used OpenAPI in their recent projects are Information Technology (100%), Product Development (92%), and Project Management (75%).
Main locations of FRATCH Experts, who have recently used OpenAPI
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 
Stuttgart Request a free demo
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FRATCH CEO
