REST API Expert in Dortmund
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Meet FRATCH Experts in Dortmund, who have recently used REST API
Oliver K.
Last position:
Founder & Manager at ThinkForm Studio – AI Product Design & Innovation
Designing AI-native digital products by combining product strategy, UX research, interaction design, software engineering, and modern AI workflows. Leading projects from discovery to implementation while integrating AI throughout the entire product development lifecycle.
Key responsibilities
- → Product discovery, stakeholder workshops, Jobs-to-be-Done and user research
- → User journey mapping, information architecture and interaction design
- → Wireframes, high-fidelity UI, prototypes and scalable design systems in Figma and Penpot
- → AI-assisted interface generation and rapid concept exploration using Figma AI, Figma Make and generative design workflows
- → Design-to-code workflows with AI-supported frontend generation and engineering collaboration
- → Building accessible interfaces following WCAG 2.2 and enterprise design standards
- → Usability testing, iterative validation and KPI-driven product optimization
- → Development of AI knowledge systems, MCP-powered design workflows and human-in-the-loop review processes
- → Close collaboration with engineering teams to ensure production-ready implementation
Arkadius S.
Last position:
AWS Pricing Platform / API & Integration Architecture at Porsche Digital
Development and evolutionary further development of a highly available, cloud-native microservice and integration architecture for dealer and retail processes in the Porsche Car Configurator.
Responsibilities
- Development of Java-/Kotlin-based backend, API, and integration components (Spring Boot)
- Integration of internal and external systems via REST/OpenAPI, GraphQL, Apache Kafka, and AWS SQS (synchronous and asynchronous)
- Implementation of stable, high-performance communication and data flows in a cloud-native platform architecture
- Processing of structured data formats (JSON, Protobuf, GraphQL schemas) based on existing API patterns
- Performance optimization of distributed microservices with reduced response times and higher operational stability
- Technical tests (unit, integration, and API tests) as well as error analysis in production-like environments
- AWS Infrastructure as Code with Terraform and AWS CDK
- CI/CD automation (build, test, and deployment pipelines) with GitHub Actions
- AI-supported feature implementation (GitHub Copilot Agent)
Label: Kotlin, Java 25, Spring Boot 4, Protobuf, TypeScript, AWS, Terraform, CDK, Apache Kafka, AWS SQS, REST/OpenAPI, GraphQL, JSON, PostgreSQL, Docker, GitHub Actions, Maven, Gradle, JUnit, Mockito, Testcontainers
Nemanja M.
Last position:
AI Engineer / Senior Backend Engineer at Intelycx
Manufacturing intelligence platform with enterprise workflows, RAG, real-time AI assistant features, and multi-repository backend architecture.
- Built and extended production AI/backend services with Django, DRF, FastAPI, GraphQL, Celery, PostgreSQL, MySQL, Redis, and WebSockets across a modular multi-repository platform.
- Contributed to ARIS V2, a real-time manufacturing AI assistant using LangChain, LangGraph, MCP tool orchestration, planning/execution flows, OpenAI, AWS Bedrock, Qdrant, and Elasticsearch/OpenSearch-backed retrieval.
- Supported rollout expansion from ARIS V1 in 4 of 17 client production plants to ARIS V2 currently active in 13 of 17 plants, increasing real-world deployment coverage to more than 50% of the client footprint.
- Worked on document-grounded RAG functionality including ingestion, OCR, chunking, embeddings, indexing, retrieval, reranking, and grounded answer generation for industrial workflows.
Stack: Python, Django, DRF, FastAPI, LangChain, LangGraph, GraphQL, Celery, WebSockets, OpenAI, AWS Bedrock, Qdrant, Elasticsearch/OpenSearch, PostgreSQL, MySQL, Redis, Docker.
Kersten L.
Last position:
Lead Architect / Lead Developer at Bettles: Sports Betting Platform
- Complete greenfield rebuild across the whole stack — built AI-native: backend in Go and NestJS, PostgreSQL (CNPG) on K3s with GitOps/Terraform; frontend on Angular 22, zoneless.
- Orchestrated coding agents (e.g. Claude Code, Cursor) across the entire lifecycle — architecture, implementation, testing, reviews, documentation — driven by Specification-Driven Development (SDD).
- “Bruno” — LLM commentator persona backed by RAG and MCP for a personality that stays consistent across all generations (match previews, post-match reports, his own virtual bets).
Angular 22 (zoneless, without Zone.js), Claude Code, Claude Code Skills, CNPG, Cursor, Design Tokens (Spec for Code), Docker, Gherkin, Git, GitLab, GitOps, Go, Google Gemini, Grafana, Hetzner Cloud, K3s, Keycloak, Kubernetes, Lighthouse, LLM Integration, Model Context Protocol (MCP), NestJS, Node.js, NPM, Playwright, PostgreSQL, Prometheus, RAG, REST, Specification-Driven Development (SDD), Structured Outputs, Terraform, TypeScript, Vitest
Laurin H.
Last position:
Software Architect (Freelance) at Care4Sure
- Delivered MVP-focused full-stack architecture for a health-sector client: Vite/React frontend, backend services on Google Cloud Run, and Supabase for database plus IAM/authentication.
- Supported product requirements engineering and prioritized cost-aware workload placement, implementing browser-side/edge computation where feasible before moving logic to backend services.
Diego E.
Last position:
RPG Software Developer from RPG III to Free Format
- Development of software and system support for RPG development.
- Development, optimization and maintenance of programs in RPG (RPG II to ILE Free Format).
- Performing integration tasks, data management as well as applying and managing system updates.
- User support and training to ensure smooth system operation.
Adnan U.
Last position:
Independent AI & Automation Projects
- Development of an automated job-scouting workflow for the aggregation and LLM-based evaluation of job postings from RSS feeds and APIs.
- Development of a Telegram bot for voice and text messages, featuring LLM-supported processing, summarization, and structured JSON output.
- Implementation of a personal task-planning assistant using n8n, OpenRouter, and Supabase for automated daily and knowledge organization.
- Development of LLM chatbots for structured knowledge retrieval utilizing prompt constraints, guardrails, and forced output formats.
Sandra R.
Last position:
FRONTEND DEVELOPER at easy Marketing GmbH
- Development and enhancement of scalable Vue.js/TypeScript applications, as well as reusable components and frontend architectures
- Development of modern, high-performance web applications for internal software solutions using Vue.js, Pinia, and Vuex
- Efficient integration and processing of data from external APIs to support frontend development and ensure smooth end-to-end functionality
- Implementation and maintenance of automated tests for quality assurance using Vitest
- Creation of interactive website prototypes in Figma and Adobe XD as a basis for Vue.js implementations
- Participation in technical reviews and code reviews to ensure high code quality and continuously improve development processes
- Use of AI-supported development tools such as ChatGPT and Claude for more efficient development, error analysis, and code optimization
- Use of CI/CD pipelines for the efficient integration of automated tests, builds, and deployments into the development workflow
Thomas G.
Last position:
Senior .NET / Cloud Engineer at Freelance
Building an observability and alerting solution for Business Central Job Queue monitoring
- Built a central monitoring solution to track the Business Central Job Queue in a multi-organization environment in Azure DevOps
- Integrated Azure Application Insights and Log Analytics for structured collection and analysis of job runtimes and error events
- Developed KQL queries for targeted analysis of failed jobs and detection of error patterns
- Connected Grafana and Power BI to visualize operational metrics and job status in real time
- Implemented an automated alerting workflow with Power Automate – when a job fails, a notification email is sent immediately
- Ensured transparency about the state of productive background processes during live operations
Result: Full transparency over failed Business Central jobs · Clear reduction in response time through automated email alerting · Stable foundation for proactive operation of productive background processes
Technologies: Azure DevOps | Application Insights | Log Analytics | KQL | Grafana | Power Automate | Power BI | Business Central | Azure Monitor
Christian W.
Last position:
Interim Business Analyst / Product Owner at Bundesdruckerei GmbH (via FourEnergy GmbH)
- Initial assessment of requirements based on a business value prioritization framework
- Identification of issues as well as requirement gathering and evaluation using UML, BPMN, and design thinking methods for iterative requirements analysis through interviews and workshops
- Use of user story mapping in Miro to visualize and align functional requirements (e.g. correct transmission of all application data and attachments to the specialist system) as well as non-functional requirements (e.g. complete and verifiable deletion of an applicant's data) with stakeholders
- Proactive stakeholder management of internal and external stakeholders from public authorities, business units, organizations, and companies
- Preparation of status reports to communicate project progress and upcoming tasks transparently
- Responsibility for a REST-based integration solution (middleware) for secure data exchange between core systems and external specialist applications; ensuring stability and performance in day-to-day operations
- Support for Product Owners in prioritizing backlog items and in product discovery
- Communication of planning to internal and external stakeholders as well as interim assumption of Product Owner tasks and responsibilities during a staff change
Volker D.
Last position:
Developer at DV-Consulting und Entwicklung Volker Döch
- New development of a web app to manage and configure counting devices for large events
- Technologies: .NET 10, C#, Blazor, MudBlazor, MySQL, Git
Mohamad A.
Last position:
Systems Engineer for Network Security at Bechtle AG
- SD-WAN solution by Aruba – Swiss energy company (330 sites): design and implementation of an SD-WAN branch solution with Aruba 9004 gateways, encrypted overlay, policy-based routing, WAN load balancing, and centralized management via Aruba Central.
- LAN/WLAN & security – schools in Germany (9 sites): deployment of Aruba switches & AP-505, FortiGate 80F firewalls; setup of Checkmk monitoring, incident and change management, and secure admin access (BeyondTrust).
- Multi-site security – energy billing company (20 sites): deployment of a complete Fortinet solution (FortiGate HA cluster, FortiSwitch PoE, FortiAP), IPsec remote-access VPN via FortiClient, centralized management via FortiCloud, IntraID authentication, operations and incident management.
- Data center migration – German client: migration of data center switches (Mellanox), firewall cluster, and OfficeConnect switches to a new data center; securing configurations, implementing HA designs, testing, monitoring, and coordinated change and incident processes. Setup of two new 6300 M VSX clustered switches.
- Data center security – university hospital: implementation of a high-availability FortiGate 400F firewall cluster across three data centers; security policy design, operational support, and change/incident management.
- Enterprise campus & network access control – manufacturing company in Germany: introduction of Aruba ClearPass NAC, setup of a VSX-based switching architecture, secure WLAN access with MPSK, and integration into existing networks.
- EU client (Germany & Poland) – Sophos firewalls: operations, incident and change management of Sophos firewalls including IPsec VPN; troubleshooting and ongoing optimization of security configurations.
- Network modernization – pharmacy client in Germany: design and rollout of core and access switching (Mellanox, Aruba Instant On), migration from Sophos to Fortinet firewalls, network segmentation, and security hardening.
Andreas E.
Last position:
AI Coach and Consultant at Studio 8 Dortmund
- Setting up and consulting a startup for organizational development (AI-supported)
- Vision and mission workshops
- Marketing roadmap and process design
- Development of sales processes (sales funnel, lead generation)
- Brand building and social media omnichannel strategies
- Content generation for audio, video, and posts (AI-supported)
- Agile consulting and SAFe implementation
- Atlassian consulting and setup of Confluence and Jira (workflows, dashboards, reporting)
- Setup of a podcast and video studio including live streaming setup
- Selection and implementation of hardware and software
- Website creation and brand building
- CMS implementation based on Typo3
- Consulting in sales, marketing, and social media
- Supporting companies in the efficient use of AI technologies
- Strategy development and consulting on implementing AI strategies
- Change management and supporting teams in AI adoption, including training
- Technical expertise in machine learning, data processing, and large language models (LLMs) like Llama, Claude, and OpenAI GPT
- Selection, fine-tuning, and integration of LLMs into business processes
- Consulting on ethics and governance for responsible AI use
- Conducting tailored training for executives and teams
- AI analysis of various large language models (Llama, OpenAI, Mistral)
- Creation and training of custom GPTs focused on organizational development (product vision, OKR, agile maturity)
- Development of a chatbot on agile maturity
- Development of an AI-generated survey to assess organizational agility
- Setup of local offline GPTs with a focus on data protection and GDPR compliance
- Conducting AI workshops for SMEs and mid-sized companies
Hamza S.
Last position:
Software Developer at WaslSign
- Designed and implemented the system architecture for scalable document workflows, improving stability and performance.
- Optimized the login flow with TOTP-based MFA, reducing complexity and login time by 35%.
- Built secure backend APIs for document upload, signing, and management.
- Developed encrypted file handling with AWS S3 pre-signed URLs, ensuring GDPR-compliant data protection.
- Implemented JWT-based role authentication, strengthening access control and overall platform security and reducing code and database complexity.
- Optimized database queries and caching using ORM, reducing API response time by 40%.
- Integrated real-time webhook updates, enhancing workflow transparency and user experience.
Yoav N.
Last position:
Freelance Software Architect at Freelance Consultant
- Various small consultations, e.g. concepts and arcitectures.
- Updating my Matlab, Linux, IPv6, Cyber-Security, C++ (up to 23) and Python skills.
Discover over 15,000 top freelancers
Statistics of experts using REST API
Aggregated from the professional profiles of matched freelancers.
Experience
18 years (Germany: 17 years)
Position duration
2 years (Germany: 2.9 years)
Positions per freelancer
13 (Germany: 12)
Top business areas
Information Technology, Product Development, Project Management
Top industries
Information Technology, Healthcare, Automotive
Certification focus areas
Information Technology, Product Development, Project Management
Bachelor's degree or higher
93% (Germany: 92%)
Master's degree or higher
50% (Germany: 55%)
Doctorate
7%
Certifications per freelancer
2 (Germany: 3)
Most common languages
German, English, Spanish
Speak two or more languages
100% (Germany: 97%)
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 Dortmund 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 Dortmund using REST API
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.
REST API 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 (95%)
- Healthcare (60%)
- Automotive (45%)
- Education (45%)
- Banking and Finance (45%)
- Manufacturing (45%)
- Professional Services (40%)
- Government and Administration (40%)
Please note that freelancers can work across multiple industries, so percentages overlap.
About the technology
What REST APIs do
A REST API is a web interface that lets applications exchange data through HTTP. It models resources such as customers, orders or documents and uses methods such as GET, POST, PUT and DELETE. JSON is common, but other representations can be supported when a project requires them.
Where they are used
REST APIs connect the products and systems that companies rely on every day:
- Web and mobile applications backed by shared services
- E-commerce catalogues, carts, orders and payment workflows
- SaaS integrations, partner portals and internal tools
- Data exchange between CRM, ERP and logistics systems
- Public APIs for customers, suppliers or third-party products
Ecosystem and tooling
Strong REST API work covers more than endpoint code. It includes HTTP semantics, status codes, pagination, filtering, validation and versioning. Professionals often use OpenAPI or Swagger for contracts and documentation, alongside Postman, automated tests, CI pipelines and observability tools. Framework knowledge may include Spring Boot, ASP.NET Core, Node.js, Django or Laravel.
When companies need specialists
Freelance expertise is useful when an existing API is unreliable, undocumented or difficult to extend. It also helps during a product launch, a system integration or a migration from tightly coupled services. In Dortmund, specialists may support industrial, retail, logistics and service businesses while working remotely or coordinating with local teams on site.
- Define a clear resource model and API contract
- Improve authentication, authorization and input validation
- Stabilize integrations with tests, monitoring and error handling
What quality looks like
A dependable REST API is predictable for its consumers. Good professionals design consistent URLs and responses, return meaningful status codes, protect sensitive data and plan backward-compatible changes. They document edge cases, test failure paths and consider rate limits, caching, idempotency and database performance instead of focusing only on successful requests.
Collaboration and delivery
A project usually starts with existing documentation, sample requests, data models and integration goals. Clear acceptance criteria make remote collaboration effective, while German or English communication can be agreed with a Dortmund-based team. The final deliverable may include an OpenAPI specification, implemented endpoints, automated tests, deployment configuration and handover documentation.
Frequently asked questions
Everything clients usually want to know about REST API, in one place.
A REST API lets software exchange resources over HTTP using familiar methods such as GET and POST. Companies use RESTful APIs to connect web apps, mobile apps, databases, SaaS products and external partners.
A RESTful API exposes resource-oriented endpoints and usually relies on standard HTTP behavior, which makes it widely understood and easy to integrate. GraphQL gives clients more control over requested fields, while SOAP offers a stricter message and contract model for some enterprise environments.
A strong REST API specialist should understand backend frameworks, relational or document databases, authentication, automated testing and deployment pipelines. Experience with OpenAPI, OAuth 2.0, Docker, monitoring and cloud services is also valuable when the interface supports production systems.
The required REST API experience depends on the scope and risk of the integration. A simple internal interface needs different depth than a public API with versioning, high availability, sensitive data and many external consumers. Assessing shipped, documented API work is more useful than relying on a generic experience label.
Yes, REST APIs are well suited to remote collaboration because contracts, requests, tests and documentation can be reviewed online. On-site workshops in Dortmund can still help when specialists must understand local processes, coordinate with hardware or work closely with non-technical stakeholders.
For a REST API project, provide the systems involved, core resources, authentication needs, expected consumers and known integration constraints. Existing specifications, example payloads, deployment details and acceptance criteria help a specialist estimate the work and identify risks early.
Review whether the REST API has consistent resource naming, appropriate status codes, clear validation and useful error responses. Also check its OpenAPI documentation, automated test coverage, security controls, observability and approach to versioning and backward compatibility.
Yes, REST API work often includes discovery, data modeling, integration design, testing, documentation and production support. Freelancers can contribute to API governance, performance improvements and migrations when they understand both the technical interface and the business process it connects.
The average hourly rate of freelancers in Dortmund, Germany who have used REST API in their recent projects is 86 €, which corresponds to a daily rate of about 685 € based on an 8-hour working day.
Of the freelancers in Dortmund, Germany who have used REST API in their recent projects, 93% hold at least a Bachelor's degree, 50% hold at least a Master's degree, and 7% hold a doctorate.
On average, freelancers in Dortmund, Germany who have used REST API in their recent projects have 18 years of professional experience, with a single engagement typically lasting around 2 years.
The most common languages among freelancers in Dortmund, Germany who have used REST API in their recent projects are German (100%), English (100%), and Spanish (20%).
The most common industries among freelancers in Dortmund, Germany who have used REST API in their recent projects are Information Technology (95%), Healthcare (60%), and Automotive (45%).
The most common business areas among freelancers in Dortmund, Germany who have used REST API in their recent projects are Information Technology (95%), Product Development (90%), and Project Management (60%).
Main locations of FRATCH Experts, who have recently used REST API
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.
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