OpenAPI Experts in Frankfurt
for reliable APIs, matched in minutes with vetted freelancers and the power of AIHire experts who design API contracts, document REST services with Swagger tools, and support integrations across cloud and enterprise systems. FRATCH finds a precise match quickly from vetted, available freelancers.
Meet FRATCH Experts in Frankfurt, who have recently used OpenAPI
Saqib J.
Last position:
AI Developer / AI Engineer (Lead) at KOM4TEC GmbH
- Designed and implemented modular AI assistants for sales and business processes within 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 servers, 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, and mentoring within 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
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 Device Manufacturer
Participation in the EU-funded MORANE-2 project to validate the Future Railway Mobile Communication System (FRMCS) in real-world use cases: preparation of the requirements specifications for TOBA and the associated test specifications.
Technologies: 5GS (Radio & Core), FRMCS, MCx (MCPTT, MCData, MCVideo), MC Gateway UE, MCx Priority/Security/QoS Management, ETCS, SIP, IMS
Felix T.
Last position:
Data Engineering and Power BI at Wesernetz Bremen
Independently built a data platform with cross-system process monitoring.
- Designed the Bronze/Silver/Gold architecture and Python-based pipelines for diverse operational sources.
- Cleaned, harmonized, and validated data; processed and stored it in Parquet format.
- Tracked data history and built business-focused fact and dimension models for traceable reporting.
- Automated data delivery with Python and Power Automate (desktop and cloud); used SharePoint for archiving and data access.
- Developed the Power BI solution from data preparation through to visualizing process statuses, work progress, and deviations.
Technologies: Python, SQL, Parquet, Power BI, Power Query, Power Automate, SharePoint, Copilot
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
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
Ralitsa P.
Last position:
Process, Project and Requirements Manager, Customer 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
- Management of the development team according to Scrum
- Design and project management of the API interface to existing tools
- Process modeling for the new Order Dispatching team (FCD & BD)
- Design of processes within and outside the team
- Requirements design and implementation of the necessary tools
- Creation and calculation of production KPIs
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.
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.
Ingo D.
Last position:
Analytics at BaFin - Federal Financial Supervisory Authority Frankfurt
- Introduction of approaches for developing and automatically deploying cloud-native software and machine learning programs 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
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
2.2 years (Germany: 1.8 years)
Positions per freelancer
15 (Germany: 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, Business Intelligence
Bachelor's degree or higher
89%
Master's degree or higher
44% (Germany: 51%)
Certifications per freelancer
2
Most common languages
German, English, Russian
Speak two or more languages
100% (Germany: 94%)
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 Frankfurt 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 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 29 Oct 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 (100%)
- 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-agnostic specification for describing HTTP APIs. It defines paths, operations, parameters, request bodies, authentication rules, responses and reusable schemas in a machine-readable format. Teams use the contract to align product, backend, frontend and integration work before services are released.
Services and Integrations
OpenAPI supports REST services for web applications, mobile products, partner portals and internal systems. A clear contract helps teams generate client libraries, server stubs, interactive documentation and validation rules. It is useful wherever different systems must exchange data consistently and predictably.
Ecosystem and Tooling
The ecosystem includes Swagger UI, Swagger Editor and Swagger Codegen, alongside tools such as Redoc, Postman and API gateways that import or validate OpenAPI documents. Strong specialists understand YAML and JSON, HTTP semantics, JSON Schema, OAuth, API keys and versioning. They also connect specifications with CI pipelines, testing and service repositories.
- Create or refine an OpenAPI contract
- Generate documentation and client SDKs
- Validate requests, responses and breaking changes
- Connect API definitions with testing and delivery workflows
When Expertise Helps
Companies often bring in freelance expertise when an API is inconsistent, undocumented or difficult for partners to adopt. Support is also valuable during a service split, a platform integration, a gateway migration or a redesign of public API standards. In Frankfurt, specialists may support local product and enterprise teams on-site, remotely or in a hybrid setup, with collaboration in English or German where needed.
Choosing a Specialist
Look for professionals who can show more than a polished specification file. They should explain design decisions, model errors and edge cases, manage backward compatibility and test the contract against a real service. Experience with authentication, pagination, webhooks and consumer feedback is a strong sign that their work will hold up beyond a demo.
Project Collaboration
An OpenAPI engagement works best when the specialist joins early enough to clarify resources, data ownership and API users. Ask how they handle reviews, governance, generated artifacts and changes across environments. Remote collaboration is practical when repositories, review rules and decision records are clear; on-site work can help when several Frankfurt teams need to agree on a shared interface.
Frequently asked questions
Before you brief your next project: the most common questions about OpenAPI.
OpenAPI is used to describe HTTP APIs in a structured document that people and tools can read. Companies use it to plan endpoints, publish documentation, validate traffic, generate client libraries and coordinate teams building or consuming REST services.
OpenAPI commonly describes REST-style HTTP interfaces with explicit paths and operations. GraphQL centers on a query schema, while gRPC uses service definitions and often relies on Protocol Buffers; the right choice depends on client needs, transport, performance and the existing system landscape.
A strong OpenAPI specialist usually understands HTTP, REST design, YAML, JSON Schema and API security. Skills with OAuth, API gateways, Postman, Swagger UI, automated testing, CI pipelines and backend implementation make the specification more useful in production.
The required experience depends on scope and risk rather than a fixed number of years. A simple internal interface may need contract design and documentation skills, while a public API or large integration usually calls for someone who has handled versioning, compatibility, governance and consumer onboarding.
Yes. OpenAPI documents work well in shared repositories with pull requests, automated validation and clear review ownership. Frankfurt teams should agree on meeting cadence, working language and access requirements so remote or hybrid collaboration remains effective.
Ask the specialist to review a sample contract and explain naming, error responses, security schemes and compatibility choices. A capable OpenAPI professional considers how consumers use the API, tests the document against implementation and keeps generated documentation aligned with the service.
OpenAPI can generate server stubs, models, documentation and client SDKs through tools such as Swagger Codegen and related generators. It does not replace business logic, data design, security implementation or operational decisions, so generated output still needs careful engineering and review.
Bring in an OpenAPI freelancer when several teams need a shared contract, an API lacks reliable documentation or an integration is producing recurring misunderstandings. Early involvement is especially helpful for public interfaces, service decomposition, gateway changes and compatibility planning.
The average hourly rate of freelancers in Frankfurt, Germany who have used OpenAPI in their recent projects is 99 €, which corresponds to a daily rate of about 791 € 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 2.2 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 (100%), 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 (100%), 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 
Dusseldorf Countries:
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