
REST API Expert
to connect products with vetted, available freelancers matched in minutesHire experts who design resource-oriented endpoints, secure integrations and document reliable RESTful services. Get specialists for API architecture, third-party connections and performance improvements through fast, precise matching with vetted, available freelancers.
Meet FRATCH Experts who have recently used REST API
Silvia B.
Last position:
Business Consultant - Product Management Banking at Aareal Bank AG
- Focus on optimizing and further developing the internal customer EBICS application
- Functional and technical consulting for Aareal First Financial Solutions AG on EBICS standard products and applications in the areas of operations and further development, as well as project-related communication with external development partners and the product manufacturer to implement the corresponding technical optimizations
- As the functional coordinator, providing advice on content-related and regulatory requirements as well as technical prerequisites and requirements, and bringing these together at the functional level
- Consulting on the use of EBICS formats
- Reviewing the current EBICS standard for optimization and further development potential
- Analyzing the current state to identify development potential and deriving appropriate recommendations for action while considering regulatory requirements
- Conducting EBICS tests throughout the project
- Functional responsibility for requirements management and, in this context, recording and documenting requirements for such tests
- Designing a functional and sustainable test management system
- Conducting and evaluating tests
- Consulting on sustainable quality assurance and audits
- Project language: German and English
- Tools/Methods: MS Project, MS Office, MS Visio, TestRail, Confluence, Jira, Business Logics Bankkrecher, Business Logics Test Data Generator, Business Logics Banking Tool, Business Logics Test System, DBEAVER, Squirrel, Unix Virtual Machines, WinSCP, Kitty, Putty, various Aareal Bank products, Online Banking Portal, Aareal Sign, core banking system, SAP Blue Eagle, SAP RE-FX, Aareon Wodis Sigma, Haufe Real Estate Wowinex, GAP Group Immotion, UTS Karthago, SAP IS-U/Waste, SIV kVASy, various EBICS clients
Kathrin S.
Last position:
Requirements Engineer at Governikus GmbH & Co. KG
- Impact: Structured requirements analysis and quality assurance as a foundation for the further development of a software solution.
- Analysis, documentation, and coordination of requirements. Conducting stakeholder analyses, interviews, and workshops to gather and validate requirements. Conducting requirements reviews and working closely with business departments and development teams.
Techniques & Tools: Requirements Engineering, Stakeholder Management, Workshop Facilitation, System Context Modeling, Requirements Reviews, Quality Scenarios, Miro, Jira, Confluence
Florian S.
Last position:
AI Product Manager / Product Owner at AI Product
- Generative AI products for corporate clients, owned from strategy through specification to production.
- Central strategy, local configuration: multi-tenant AI assistant for occupational pension schemes (bAV), delivered as an interactive avatar with text and voice path. Three tenants run on one codebase, each with its own conversation guide, while the knowledge base, guardrails and escalation paths stay central
- Versioned, AI-ready knowledge base composed into a tenant-agnostic voice context and tenant-specific text prompts — the configuration layer that keeps local adaptation from forking the product
- Conversational design: answer limits, scope and off-topic handling, anti-hallucination rules, escalation and lead handover to human advisors
- Five eval suites as a quality gate before any prompt or model change (anti-hallucination, LLM-as-judge failure modes, multi-turn consistency, voice KPIs, action vocabulary with confusion matrix); user test with 10 testers (Hamburg, 07/2026) drove the rework from alpha to beta
- Coordinated external developers, compliance and client stakeholders; GDPR-compliant EU stack, IDD-compliant, EU AI Act classification documented
- Second product line: white-label social media generator for consultancy chilli mind (CH/DE) — one codebase, per-client branding and configuration
- Results: 239+ deployments and a pilot with corporate customers · 108+ deployments for the white-label product · repeatable pattern for multi-tenant AI products in a regulated environment
Gabin Maxime N.
Last position:
Multi-Agent R&D Pipeline (3 Custom Agents) at Independent Project
Claude Code subagents, MCP, Pydantic V2, pytest, bandit
Designed and shipped 3 specialized agents that hand work down a line: a research agent writes a cited implementation spec, a coding agent builds the modular code and its tests, a review agent ranks findings by severity and applies the fixes. Each handoff is a structured document, so no stage depends on another agent's context window.
Connected the research agent to an academic-research MCP server (Semantic Scholar, ArXiv, Hugging Face Hub, citation snowballing) so every reference traces to a tool result rather than the model. Gated commits behind ruff, mypy, pytest and bandit, required human sign-off before installs and commits, and persisted session state on disk so long runs survive a context reset.
Patrick L.
Last position:
Senior GenAI Fullstack Developer at SBH (Schulbau Hamburg)
Remote freelance role focused on Agentic AI strategy, secure application patterns, and reusable agentic workflows for a government agency.
- Development and implementation of an open-source Agentic AI strategy for a government agency, with a focus on GDPR, security, and self-hosted solutions
- Development of reusable agentic workflows and business applications that enable non-technical employees to solve business problems independently
- Implementation of nine business applications with Single Sign-On (SSO) and Azure PostgreSQL integration on Hetzner Linux servers
Techstack: Python, Streamlit, Anthropic SDK (Claude), Azure, Linux, PostgreSQL, MS SQL, Angular
Onur K.
Last position:
Project Manager & Outsourcing Manager at SENEC GmbH (EnBW Group)
- Built a scalable nearshore IT developer hub (Croatia, Czech Republic, Poland) as an independent company through a BOT model (Build – Operate – Transfer)
- Identified, selected, and managed full-service agencies; introduced management and control mechanisms, including KPIs, SLAs, and regular service reviews
- Prepared and reviewed data processing agreements and framework contracts in coordination with Legal & Compliance; integrated regulatory requirements (including KRITIS) into process design
- Advised on cloud vs. on-premise strategies, data storage, and authorization concepts; supported Procurement with tendering and service provider evaluations
- Managed change and process harmonization between internal teams and nearshore partners; reported to executive management, CFO, and CIO
Result: Scalable IT developer hub with an audit-ready governance model, reduced operating costs, and accelerated product development.
Ornel Franck W.
Last position:
Sales Partner at ERGO PRO
- Industry: Insurance, Trade, IT
- Customers & Projects: Consulting and selling insurance and similar services
- Main tasks: Insurance consulting (health insurance, retirement planning, wealth building); commercial services, inside and field sales; sales data analysis and forecasting; customer consulting and support; opening a new sales headquarters for private and business customers; business development & innovation management; business use case development; process optimization; stakeholder management; team leadership and training; preparation and delivery of trainings;
- Technologies used: Microsoft Office 365, Microsoft Teams, Jira, Draw.IO, Camunda 8, Java (8, 17,21,25), Git, Spring Boot, Spring Batch, Spring Data REST, Spring Web, Spring Security, J-Unit, Playwright, Lombock, Vaadin, H2, PostgreSQL (16, 17 18), pgAdmin, Docker, LLMs, JasperSoft Studio, JasperReports
Thomas P.
Last position:
Product Owner & AI Automation Architect (B2B) at Ihre-Hygieneberatung
Development of a digital audit application for inspections in medical facilities. The goal is to connect on-site data collection, voice recording, documentation and downstream processes in one end-to-end, AI-supported workflow.
Design and development of a Flutter audit app with Claude Code for the structured execution and documentation of inspections.
Processing of voice recordings captured in the app through automatic transcription and AI-supported creation of structured inspection reports, followed by an approval process
Connecting various data sources such as email, Odoo 19, attendance records and Google Drive via n8n to automate billing and follow-up processes
Automatic provision of required documents and email delivery through n8n-controlled workflows, including the use of LLMs for text creation
Skills: Flutter, Claude Code, LLM Integration, n8n, Odoo 19, Google Drive, Process Automation
Ebru A.
Last position:
Product Analytics & App Tracking Consultant at EnBW mobility+ AG & Co. KG
- Product Analytics, Mobile App Tracking & Tracking Governance (B2C Mobility App) – agile project management (Scrum/Kanban)
- Product Ownership for Product Analytics and Mobile App Tracking of the EnBW mobility+ app; gathering, prioritizing, and translating business requirements into actionable concepts and Azure DevOps user stories with acceptance criteria.
- Derivation of tracking requirements when introducing new app features (including Resilient Map), definition of tracking parameters (screens, events, custom definitions), and ensuring privacy-compliant tracking (Firebase, GA4, Adjust) based on the tracking concept.
- Design and adaptation of dashboards and funnel reporting for campaigns (GA4 validation, onboarding and order flow analyses, conversion funnels, charging start flow) to identify drop-off points and optimization potential.
- Management of the technical raw data export (Adjust to BigQuery) and connection to the data warehouse/data lakehouse, including data mapping; collaboration with international development teams, Data Engineering, Marketing/Sales, and Product Management.
- Establishment of standardized tracking architecture, naming conventions, and governance; analysis and expansion of tracking (new features and “blind spots”), test design, handover to testers, and quality assurance and approval before releases; documentation in Conceptboard.
Wolfgang O.
Last position:
Project Manager at EnBW - Netze Südwest
- New development and further development of the existing MS Dynamics CRM
IT systems: Microsoft Dynamics Customer Service, SharePoint, DevOps, SAP IS-U
- CRM implementation / further development
- Taking over from the previous service provider
- Business process analysis
- Agile project organization
- Business analysis / requirements engineering with AI support
- Use of AI in development
- Analysis of master data processes
- CRM customer data management
- Requirements documentation
- Stakeholder management
- Workshop moderation
Peter S.
Last position:
Senior ML Engineer & AI Researcher at Anonymous Client
Project: Defect Generation on Test-Bench Images of Metal Surfaces Environment: Automated Visual Inspection (AVI), Metallurgy & Manufacturing
- Objective & Implementation: Designed, architected, and trained Generative Adversarial Networks (Pix2PixHD / SPADE) for image-to-image transformation. Targeted generation of synthetic material defects (e.g., cracks, inclusions, scale) on rough metal surfaces under real test-bench lighting conditions for privacy-compliant and efficient dataset expansion (data augmentation).
- Technical Design: Implemented robust Generative AI and computer vision pipelines in Python and PyTorch. Used semantic segmentation approaches for mask-controlled defect synthesis and subsequent evaluation with EfficientDet object detection models.
- Business Impact: Massive dataset upscaling (10x) without time-consuming and costly physical test-bench runs, while significantly improving the detection performance of automated inspection systems.
Technologies & Skills Used: Python | PyTorch | SPADE | Pix2PixHD | EfficientDet | Machine Learning | Semantic Segmentation | Computer Vision
Khalid E.
Last position:
Lead Architect & Developer at kem-consulting
Development of an agent-based governance platform for the automated assurance of EU AI Act compliance and ODA-compliant orchestration of AI services in complex enterprise environments.
Design and implementation of an agent-based "Mission Control" framework (Aletheia Conductor) for autonomous state monitoring and process control.
Development of "Compliance-as-Code" (CaC) solutions based on OPA/Rego for system-wide enforcement of regulatory guardrails.
Integration of TM Forum ODA standards (TMF630, TMF622, TMF642) to ensure interoperability and standardization.
Building a highly available event-driven architecture using Redpanda and CloudEvents v1.0 for near-real-time event processing.
Implementation of an audit-proof "Evidence Chain" through cryptographic linking of trace logs in preparation for automated audits.
Tech Stack: Java 21 (Quarkus Native), TypeScript (Next.js), Redpanda (Kafka API), CloudEvents v1.0, OPA (Open Policy Agent) & Rego, TimescaleDB, ZincSearch, Redis, TM Forum ODA, Git, GitHub, Clean Code Development, Like-C4.
Stefan O.
Last position:
Founder at ProtocolEngine.io
Evidence-led health intelligence platform turning published research into personal health protocols. It scores 430 habits, foods, and supplements against the studies behind them, and moves the score when the evidence moves. Built solo.
- Built the daily ingestion pipeline across PubMed, bioRxiv, and medRxiv: 43,000+ papers from 3,400+ journals processed into 230,000+ typed evidence claims, each one traceable back to the study it came from.
- Designed the six-factor evidence scoring model and the public changelog behind it, so no recommendation ever appears without the papers underneath it. 23,000+ grade changes recorded and explained to date.
- Shipped an entity information model connecting every intervention to its mechanisms, biomarkers, and outcomes: 118 biomarkers with region-specific reference ranges, 77 mechanisms, 32 graded outcomes.
- Built the personalisation layer: blood panel ingestion that reads lab PDFs with a vision model and corrects results for draw time against the user's wake anchor, plus Oura, WHOOP, and Withings integration for daily readiness context.
- Operate eleven specialised review agents over the corpus and codebase, covering paper curation, retrieval quality, health-claim compliance across EU and US regimes, and security.
- Shipped the Evidence Assistant, a RAG assistant that answers from the claim database and cites the underlying papers, plus a B2B practitioner tier, an Expo React Native app, and localisation across 3 languages and 7 markets.
Stack: Next.js 16, TypeScript, Supabase, pgvector, Anthropic Claude, Vercel, DeepInfra.
Kiriakos K.
Last position:
Tech Lead / Architect : OTTO API Platform at OTTO
Maturing their API practices on both a business and technology level. My role covers strategy, architecture, developer advocacy as well as hands-on software engineering, enabling both technical teams and business leadership to adopt and act on API-centric principles effectively. Coincidentally, we also establish GitOps, DX and platform best practices with this project.
Highlights:
- Aligning executives with the initiative by clarifying strategy, replacing misconceptions and myths with facts, clarifying the value of existing assets and enabling informed decision-making
- Formulating a way forward for API Lifecycle Management at OTTO
- Driving platform progress and fostering developer engagement by hands-on engineering work towards strategic goals
API Lifecycle Management, Team Topologies, Organizational Evolution, Regulatory, Platform Advocate, Developer Platform, Communities of Practice, Terraform, Kotlin, Kafka, Kong, WSO2, Apigee, Gravitee, Backstage, AsyncAPI, OpenAPI, API Design, AWS, React, Node.js, TypeScript, Redocly, reactive programming, CDC, Golang, Gin, GitOps, DX (developer experience), stakeholder management, roadmaps, workshops, discovery.
Sascha B.
Last position:
Web Developer at GxPlex
- Built a customized MediaWiki instance, including installation, MySQL database, SSL, and automatic backups
- Set up user roles (Admin, Mod, Verified, User) and a permissions system
- FlaggedRevisions for editorial review workflows · Commenting and rating extensions
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
92%
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 26 Sep 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 26 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%)
- Banking and Finance (44%)
- Automotive (39%)
- Manufacturing (36%)
- Retail (36%)
- Professional Services (31%)
- Healthcare (31%)
- Education (28%)
Please note that freelancers can work across multiple industries, so percentages overlap.
About the technology
What REST APIs do
REST API means Representational State Transfer application programming interface. It lets software exchange resources over HTTP using familiar methods such as GET, POST, PUT and DELETE. Companies use RESTful APIs to connect web applications, mobile products, internal systems and external services through clear, stateless requests.
Where they fit
REST APIs support customer portals, commerce systems, booking flows, payment connections, content services and data exchanges between business systems. They can expose orders, accounts, catalogues or operational records while keeping the user interface separate from backend logic.
- Connect web and mobile applications
- Expose business data through versioned endpoints
- Integrate payment, identity and SaaS services
- Support partner and internal system access
Ecosystem and tooling
Strong REST API work spans HTTP, JSON, authentication and structured error handling. Experts commonly use OpenAPI or Swagger for contracts and documentation, Postman for request testing, and tools such as Node.js, Java with Spring Boot, Python, .NET or PHP on the service side. Databases, queues, gateways and cloud infrastructure also shape the implementation.
When companies need help
Companies bring in freelance expertise when a new service must be exposed, an existing interface is unreliable, or several systems need a controlled integration layer. Specialists can clarify resources, define endpoint contracts, introduce versioning and improve observability without disrupting consumers.
- Replace inconsistent or undocumented endpoints
- Prepare an API for external partners
- Add authentication, authorization and rate controls
- Test compatibility and contract changes
What quality looks like
A dependable REST API has predictable URLs, appropriate HTTP status codes, consistent payloads and useful documentation. It validates input, protects sensitive data and returns errors that clients can act on. Good professionals also consider idempotency, pagination, caching, backward compatibility and monitoring before the service reaches production.
Choosing the right specialist
Look for experts who can explain trade-offs between RESTful APIs, GraphQL and SOAP in the context of the product rather than promoting one approach blindly. Ask for evidence of integrations with comparable security, data and availability needs. Remote collaboration works well when contracts, decisions and test cases are documented; on-site work may help when the API connects to sensitive legacy systems or closely coordinated teams.
Frequently asked questions
Before you brief your next project: the most common questions about REST API.
A REST API lets applications exchange resources through HTTP, often using JSON responses. Companies use it for web and mobile backends, partner integrations, internal services and connections to external products.
A REST API usually exposes resource-oriented endpoints with established HTTP methods and caching patterns. GraphQL gives clients more control over requested fields, while SOAP provides a stricter message and contract model that can suit some enterprise environments.
A strong REST API specialist should understand HTTP, JSON, databases, authentication, authorization and automated testing. OpenAPI documentation, API gateways, observability, cloud deployment and familiarity with a backend language are also valuable.
The required REST API experience depends on risk and scope, not simply endpoint volume. A straightforward internal service may need focused implementation skills, while public, regulated or highly integrated services require proven judgment around security, versioning, resilience and compatibility.
Yes, REST API work is often suitable for remote collaboration because contracts, schemas, tests and documentation can be shared clearly. On-site coordination can still help when the service depends on private networks, legacy systems or frequent workshops with several teams.
Review whether the REST API has consistent resource naming, correct status codes, clear errors, secure access controls and reliable automated tests. Ask the specialist to explain versioning, observability, backward compatibility and how failures are handled.
A REST API freelancer can help when a team is launching an integration, restructuring unclear endpoints or preparing an interface for external consumers. Specialists are also useful for audits, security improvements, documentation and performance work when internal capacity is limited.
A REST API expert may deliver endpoint designs, an OpenAPI specification, implementation code, authentication flows, automated tests and deployment guidance. Good handover material also explains error behavior, versioning, example requests and operational monitoring.
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, 92% 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 (97%), English (96%), and French (15%).
The most common industries among freelancers who have used REST API in their recent projects are Information Technology (95%), Banking and Finance (44%), 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 (56%).
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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