REST API Expert
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Meet FRATCH Experts who have recently used REST API
Michael H.
Last position:
Interim Head of IT / Transformation Manager at A German medium-sized industrial distributor, B2B e-commerce
Agile Transformation: introducing agile principles and transforming traditional IT departments into Scrum and Kanban teams
IT Operating Model: redesigning the IT organization and introducing modern delivery structures and roles
Flight Levels: building up Flight Levels practices within IT to align strategy, coordination and operational execution
Leadership & Coaching: recruiting Agile Coaches and coaching Scrum Masters and IT leaders
ERP Operations: acting as Interim Product Owner for the existing ERP landscape and ensuring business continuity
ERP Transformation: reorganizing and supporting the ERP migration as a Project Manager; Phase 1 (financial accounting) live since October 2025
Operational Core (ERP): establishing dedicated teams for ERP Support, Feature Development, and ERP Migration
Modern Workplace: initiating the transition towards a Microsoft 365-based cloud workplace environment
Integration: establishing a dedicated team to drive integration and connectivity initiatives
Warehouse Operations: building a cross-functional team to support logistics and warehouse-related capabilities
Maintenance & Operations (M&O): introducing a dedicated team for system engineering, security, stable operations and continuous improvement
AI Initiatives: identifying and promoting practical Artificial Intelligence use cases across the IT department
As Interim Head of IT for a German medium-sized industrial distributor, I am responsible for 31 IT employees and lead the digital and organizational transformation, reporting directly to executive leadership. I took over an IT department with almost no basic structures – no clear roles, processes, documentation or ticket system – and with significant technical debt that tied up most of its capacity. Introduced agile principles and ways of working in the IT organization and transformed the traditionally structured IT department into cross-functional Scrum and Kanban teams focused on transparency, collaboration, and customer value delivery.
Redesigned the entire IT organization by establishing a modern operating model, introducing new roles such as Product Owner, Scrum Master and Solution Architect and strengthening the organization through strategic hiring and targeted capability development. Recruited and onboarded Agile Coaches to accelerate the transformation and personally managed and coached Scrum Masters as well as IT department leaders to foster servant leadership, self-management and a culture of continuous improvement.
Aligned IT-internal planning across eight teams to three Flight Levels based on Klaus Leopold (strategy, coordination, team), laying the foundation for later company-wide portfolio management. Consolidated the backlog of more than 10 workstreams and prioritized it by business value and cost of delay. Introduced a ticketing system to increase transparency and enable data-driven decision-making, flow-based work management, and greater accountability at all levels.
Established and supported multiple cross-functional teams, including the Operational Core (ERP) domain with dedicated streams for Support, Feature Development and ERP Migration, as well as teams responsible for Warehouse Operations, Maintenance & Operations (M&O) including system engineering and security, Modern Workplace, Data Quality and integration initiatives. Worked closely with Agile Coaches to support team development, remove impediments, and continuously improve delivery effectiveness.
Acted as Interim Product Owner for the operation and enhancement of the existing ERP landscape while supporting the ERP migration as a Project Manager. Reorganized the project organization and had the already negotiated contract with the implementation partner realigned with a focus on approach and overall responsibility; Phase 1 (financial accounting) has been live since October 2025. Collaborated with the selected implementation partner to design and establish the project organization and target operating model for the ERP transformation, introducing agile delivery structures and ways of working. Facilitated the alignment between business, IT and the external vendor and played a key role in negotiating the contractual framework and delivery model to ensure a sustainable foundation for the transformation program.
Initiated the strategic modernization of the workplace environment through the adoption of Microsoft 365 cloud capabilities, establishing the foundation for enhanced collaboration, scalability and future digital services.
Launched AI initiatives to identify practical business use cases and promote the responsible adoption of Artificial Intelligence across the IT department. Encouraged self-management and empowered teams to take ownership of decisions, delivery and continuous improvement.
Michael F.
Last position:
Platform Architect (Project lead) at Würth IT
I designed and built a self-service AWS platform for Data Science teams with little or no infrastructure-as-code experience. A team writes about 10 lines of Python and gets a deployable stack with full SDLC release cycle that already follows the governance rules. Networking, encryption, IAM and tagging are decided by the platform, not by each team.
New teams or AWS accounts are onboarded with one pull request. Waste prevention and cost control is built into the defaults: Data scientists don't need infrastructure skills.
- Construct library (AWS CDK, Python). Built a versioned catalog of about 20 hardened constructs for being used in data-science projects with ML context
- Governance as code
- Multi-account, multi-tenant
- Golden-path scaffolding
- CI/CD and supply chain. Built reusable GitHub Actions workflows
- Release engineering
- QA with e2e, contract testing and unit test coverage with each release candidate
Lutz E.
Last position:
Freelance Software Developer – GoPro MultiCam Control via COHN at Plutos Company UG
- Developed a pilot system to control and monitor multiple GoPro cameras
- Implemented start, stop, status, media, download and diagnostic functions via COHN endpoints
- Built camera detection, individual and group control, and stable session/KeepAlive logic
- Set up a download pipeline with a queue, retry handling and temporary files
- Ensured consistent session, folder and file naming for multicamera recordings
- Integrated provisioning, certificates and network operations
Michael S.
Last position:
IT & Test Consultant at Testing Experts GmbH
AI Readiness - Part 3: Creating an e-book on the use of AI in software testing
- Designed and created an e-book on the sensible and safe use of AI in software testing from the perspective of an experienced test expert.
- Used generative AI (ChatGPT, Perplexity Pro) as a sparring partner for structuring, wording suggestions and creating variations, with all content finally reviewed and approved using my own expertise.
- Developed practical insights into the opportunities and risks of AI in testing, with a special focus on collaboration between testers and AI instead of “tester vs. AI”.
- Title: “11 starke Gründe: Dream-Team statt Rivalen - Tester und KI sind gemeinsam unschlagbar”
- Subtitle: “Wie Mensch und Maschine im Softwaretest das perfekte Team bilden – und warum reines KI-Testing riskant ist.”
- Planned use of the e-book as a basis for workshops, customer meetings or internal training.
- Technology: Generative AI, ChatGPT, Perplexity Pro, Microsoft Word, Adobe Acrobat, many years of hands-on professional testing experience, common sense.
Timo H.
Last position:
Software Developer at Smiths Detection
- Extension of a Swing-based UI for recording Security Restricted Articles during baggage screening.
- Introduction of a new workflow for recording Deboarding Events.
- Extension of the reporting system for Security Restricted Articles and Deboarding Events.
- Implementation using JBoss Wildfly, PostgreSQL, spring-boot 3.x, Java 8/21, Swing, JSF, JAX-RS/Resteasy, Docker, Maven, Kiro.
Franz B.
Last position:
Product Development (AI) at Self-initiated
AI phone assistant platform
Claude Code, Google AI Studio, Python, LLM / Voice-AI, PostgreSQL
- Designed and hands-on developed an AI-powered phone assistant platform (Voice-AI / LLM)—from idea and architecture through to MVP/product.
- Built agentic workflows and end-to-end automations with Claude Code and Google AI Studio.
- Also supported AI-powered delivery in client engagements: using Claude Code for governance documentation, requirements drafts, and automations.
Jörg T.
Last position:
Consultant, Requirements Engineer and Database Expert
Project – Evaluation and development of databases for a new product line for a measuring equipment manufacturer
- Current-state analysis
- Requirements analysis of the data storage layer
- Writing benchmark tests
- Design of the new database schema
- Database migrations
- Development of audit logging and Part11
- Creation of backup and recovery concepts
- Design of the persistence layer API
- Writing unit tests
- Creating requirements in Azure
Tools: C#, Visual Studio 2022, Azure DevOps, SonarQube, Git, RestSharp, WebServer, PostgreSQL, MS SQL, SQLite, MinIO, Podman, Docker, DataGrip, SQL Management Studio, HeidiDB, pgAdmin
Reinhold M.
Last position:
Business Requirements Engineer, Proxy Product Owner, Tester at AXA Konzern AG
Working Environment
- Insurance / Claims Management (Property, Liability, Automotive)
- REST-based ClaimAPI with Guidewire ClaimCenter
Scope
- Further development of the internal REST-based ClaimAPI with Guidewire ClaimCenter as the backend and various portals/front-end offices as clients, and with the following objectives: + increased AI-supported claims processing outside of Guidewire ClaimCenter + and support for all lines (property, liability, automotive).
- Further development of automated claims processing
Activities
- Interfacing IT & Business
- Design activities with documentation in Confluence, Jira: + Requirements engineering (functional and non-functional) + Design of REST endpoints and coordination with interface partners (esp. AI-colleagues) + Identification, design and evaluation of alternative solutions (moving away from a monolithic approach toward fine-grained endpoints, with code reuse across all lines if possible) + Creation / refinement of product backlog items in Jira, i.e. epics, user stories and tasks, incl. alignment with developers & POs during (pre-)refinement sessions + Using AXA Secure GPT when creating / refining user stories (description, acceptance criteria) and designing REST endpoints + Estimation and prioritization of user stories and tasks during Sprint Planning sessions + Coordination and support during the implementation of Product Backlog items + Driving decision making with preparation and presentation of decision-making documents
- Quality assurance: + Test management, including test case creation using Xray in Jira + Test execution using Bruno as REST client and in Guidewire ClaimCenter + Submission of test artifacts for PO approval + Analysis of production bugs
Methods Big Room Planning (aka PI-Planning in SAFe), Scrum, BPMN, EPK, UML, ERM, DDD
Tools / Tech Stack Teams, Confluence, Jira with Xray, OpenAPI/Swagger, REST, JSON, XML, MS Office, Bruno, GitHub repository (reading), Guidewire ClaimCenter, AXA Secure GPT (AXA's in-house GenAI solution based on Azure OpenAI)
Robert D.
Last position:
Java Software Architect at adesso insurance solutions GmbH
Paul W.
Last position:
Enterprise Architect at ePrimo GmbH
Led the end-to-end integration and migration architecture for decommissioning SAP IS-U market communication and transitioning to Salesforce Marketing Cloud (SFMC) with E.ON IT Services — covering regulated EDIFACT market messaging, a three-phase data migration (transfer of market message inventory after cutover), redesign of market communication processes, and full GDPR and German energy-market compliance.
- Designed the three-tier target architecture (SAP IS-U → NScale B2B gateway → SFMC) processing 50,000–100,000 EDIFACT messages daily within sub-5-minute SLAs.
- Architected the three-phase data migration: 36 months of historical data, zero-loss cutover of in-flight market messages, and near-real-time CDC synchronization.
- Delivered secure, BDEW/GDPR-compliant integration (AS2/OFTP2, RFC/IDoc, REST APIs, OAuth 2.0, Azure AD, AWS S3) achieving >99.5% uptime, <0.1% migration discrepancy, and RTO <4 hours.
- Applied BPMN to model and optimize the market communication processes.
Technologies: SAP IS-U, NScale, Salesforce Marketing Cloud, EDIFACT, OAuth 2.0, Azure AD, AWS S3, BPMN, Jira, Confluence, Draw.io
Fadi S.
Last position:
Data Scientist at E-Commerce
- Designed and developed a production-ready data platform based on Microsoft Fabric for an e-commerce company
- Built a scalable Medallion Architecture (Bronze, Silver, Gold) with Lakehouse and Delta Lake as the foundation for analytics and AI applications
- Developed a metadata-driven ETL platform with PySpark and a generic Incremental Loading Framework (SQL Server → Bronze → Silver → Gold)
- Developed reusable components for Microsoft Fabric Notebooks to standardize data integration, transformation, and validation
- Implemented automated data pipelines including monitoring, logging, error handling, and Delta MERGE strategies for stable production operations
- Built a business layer architecture for reporting, data warehousing, and reusable data products
- Integrated heterogeneous data sources via SQL Server, REST APIs, Amazon SP API, and Google Analytics 4
- Worked closely with business departments to analyze business requirements and translate them into scalable data architectures
Technologies: Microsoft Fabric, PySpark, Python, SQL Server, Delta Lake, Lakehouse, OneLake, Data Factory, Data Warehouse, REST APIs, Amazon SP-API, Google Analytics 4
Vaios K.
Last position:
Product Manager & Strategic Advisor at Freelance, Lovable, Dreamarium
- Advise early-stage startups on product vision, roadmapping, and GTM strategy, combining PMP and Stanford PM training with hands-on technical execution.
- Lovable: built and led a 200+ member community program for AI-native founders, bridging real-time founder feedback into product roadmap decisions.
- Lead customer discovery and OKR design engagements, scoping AI integration opportunities across client products.
David B.
Last position:
TypeScript Developer & UX Designer at colle-il-diaccino.de
TOURISM
colle-il-diaccino.de · Holiday Accommodation
- Designed and developed the website: interactive site map, accommodation comparison, and image galleries.
- Implemented German, English, and Italian language versions. Set up inquiry forms with input validation and spam protection, language-specific SEO metadata, and automated tests.
Stack: Next.js, React, TypeScript, Tailwind, next-intl, React Hook Form, Zod, Resend, Playwright, Vitest
Niko S.
Last position:
Developing Architect, Technical Lead "gridlytics" at HH Energienetze
- Built a data integration platform for high-, medium- and low-voltage assets to enable contextual analysis of time series with master data from SCADA control systems (IEC 60870 104), INIS and SAP.
- Responsible for the architecture and implementation of the solution, and acted as a sparring partner for the Product Owner.
- Technologies used: Kotlin, Spring Boot, Maven, TimescaleDB, PostgreSQL, liquibase, Elements IoT, Docker, Kubernetes, Grafana, Python, jupyter and various API gateways.
Jens L.
Last position:
Consulting Digital Development & Transformation at European Mar GmbH
Developed the product vision and outcome strategy for a new registry platform, designed a management workshop for strategic alignment, conducted BPMN process mapping across systems and roles, analyzed user story practices and further developed them on an outcome basis, and brought together stakeholders from business departments, management and the external development partner.
Skills: Product Strategy, Outcome Roadmapping, Stakeholder Workshops, BPMN/Process Analysis, Miro, Linear
Discover over 15,000 top freelancers
Statistics of experts using REST API
Aggregated from the professional profiles of matched freelancers.
Experience
17 years
Position duration
2.9 years
Positions per freelancer
12
Top business areas
Information Technology, Product Development, Quality Assurance
Top industries
Information Technology, Banking and Finance, Automotive
Certification focus areas
Information Technology, Product Development, Project Management
Bachelor's degree or higher
91%
Master's degree or higher
55%
Doctorate
7%
Certifications per freelancer
3
Most common languages
German, English, French
Speak two or more languages
97%
Based on our profile pool as of 5 Nov 2026.
Daily rate distribution
The chart shows how the daily rates of experts in this technology 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 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 5 Nov 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%)
- Banking and Finance (45%)
- Automotive (39%)
- Manufacturing (37%)
- Retail (36%)
- Professional Services (32%)
- Healthcare (31%)
- Education (28%)
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 standard HTTP requests. It commonly uses resources, URLs, methods such as GET, POST, PUT, and DELETE, and formats such as JSON. Companies use REST APIs to connect user interfaces, mobile apps, internal services, partner systems, and external platforms.
Where they are used
REST APIs support digital products across commerce, finance, healthcare, logistics, media, and SaaS. They expose controlled business capabilities without tying every client to the same application code.
- Connect web and mobile applications to backend services
- Create partner and public API integrations
- Link payment, identity, messaging, and data platforms
- Break large applications into communicating services
Ecosystem and tooling
Strong REST API work covers more than endpoint creation. Professionals use frameworks such as Express, Django REST Framework, Spring Boot, Laravel, or ASP.NET Core, alongside databases, queues, gateways, and cloud infrastructure. OpenAPI, Swagger, Postman, automated tests, Git, and CI pipelines help teams document, verify, and release interfaces safely.
When companies need specialists
Freelance expertise is useful when an API must be created, modernized, or stabilized without slowing the product team. Specialists can audit an existing RESTful API, define resource models, introduce versioning, improve error handling, or prepare an interface for external consumers.
- Replace fragile point-to-point integrations
- Define consistent endpoints and response contracts
- Improve latency, observability, and resilience
- Secure access with OAuth 2.0, JWT, or API keys
What good delivery includes
A dependable REST API has clear contracts, predictable status codes, useful errors, and consistent validation. Quality professionals consider idempotency, pagination, filtering, rate limits, caching, backward compatibility, and access control. They also produce documentation that client teams can follow without repeated clarification.
How to assess expertise
Review examples of APIs that serve real clients, not only isolated prototypes. Ask how the professional handles authentication, sensitive data, breaking changes, performance limits, and contract testing. A strong specialist explains trade-offs in plain language, works effectively with product and frontend teams, and leaves behind tests, documentation, monitoring, and maintainable code.
Frequently asked questions
Before you brief your next project: the most common questions about REST API.
A REST API lets software exchange data and trigger actions over HTTP. Companies use it to connect browser and mobile interfaces with backend services, databases, payment providers, identity systems, and partner applications.
A RESTful API exposes resources through conventional HTTP endpoints and is widely understood by web tooling. GraphQL gives clients more control over requested fields, while gRPC is often chosen for efficient service-to-service communication; the right option depends on client needs, contracts, and infrastructure.
A strong REST API specialist usually understands backend frameworks, SQL or NoSQL data stores, authentication, automated testing, cloud deployment, and observability. Experience with OpenAPI, Swagger, Postman, CI pipelines, queues, and API gateways is also valuable.
The scope matters more than a fixed number of years. A REST API project with a few internal endpoints may need focused implementation skills, while a public interface requires deeper knowledge of security, versioning, backward compatibility, performance, documentation, and operational support.
Yes, REST APIs are well suited to remote collaboration because contracts, schemas, tickets, repositories, and test environments can be shared online. Teams should agree on communication routines, review practices, environments, and language expectations before work begins.
Assess whether a REST API has consistent resources, methods, status codes, validation, error responses, authentication, and documentation. Ask to see tests and discuss how the professional handles pagination, idempotency, monitoring, rate limits, and breaking changes.
A RESTful API specialist can help when an integration is blocking delivery, an existing interface is inconsistent, or an internal team lacks capacity for secure API design. Freelancers are also useful for audits, migration work, performance improvements, and preparing an API for external partners.
A capable REST API professional should provide working endpoints, a clear contract, automated tests, authentication configuration, and deployment guidance. Depending on the project, the handover may also include OpenAPI documentation, monitoring setup, migration notes, and examples for client teams.
The average hourly rate of freelancers who have used REST API in their recent projects is 92 €, which corresponds to a daily rate of about 738 € based on an 8-hour working day.
Of the freelancers who have used REST API in their recent projects, 91% hold at least a Bachelor's degree, 55% hold at least a Master's degree, and 7% hold a doctorate.
On average, freelancers who have used REST API in their recent projects have 17 years of professional experience, with a single engagement typically lasting around 2.9 years.
The most common languages among freelancers who have used REST API in their recent projects are German (98%), English (96%), and French (16%).
The most common industries among freelancers who have used REST API in their recent projects are Information Technology (95%), Banking and Finance (45%), and Automotive (39%).
The most common business areas among freelancers who have used REST API in their recent projects are Information Technology (99%), Product Development (93%), and Quality Assurance (55%).
Main locations of FRATCH Experts, who have recently used REST API
Our freelancers and interim experts are at home all over Germany — available on-site in Berlin, Hamburg, Munich and every major business hub, or fully remote. Choose a city to discover matched specialists, local market insights and up-to-date availability.
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Frankfurt 
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Dusseldorf 
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Dortmund 
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Graz 
Zurich 
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