Sabahattin Kunas-Senior Java Developer | Lead Developer | Architect | Team Lead
Check rate
Experience
Fullstack Developer
Swisslife
Role: Senior Developer, Architecture, Lead Developer
Senior Developer: Monolith → REST Architecture Redesign of several EJB monoliths into scalable REST services. Architecture, schema and framework decisions (OpenAPI, Flyway, Camunda) while keeping the legacy interfaces. OpenAPI · Camunda · Flyway · EJB → REST
Senior Developer: New development of InvestEasy Financial retirement advisory software (2nd/3rd pillar) in line with Swiss regulations: tax country, origin of funds, beneficiaries, citizenship. Fund selection based on risk profiling. Spring Boot · Quarkus · React · TWIN signature · video identification · OpenAPI · Camunda
Team Lead: Redesign of mortgage financing Migration EJB → microservices with direct REST calls for external partners (before: email). Incident reduction from ~100 to 2–5 per week through Visitor pattern and type-safe data validation in pure Java. REST · Microservices · Design Patterns · Clean Code
Developer / Architecture: Partner portal – Lead Developer & operations (approx. 2400 active users) Sole responsibility for further development and operation of the broker platform (commissions, employee administration, customer master data). Liferay migration to 2026.Q1, Onelogin OIDC, React frontend redesign, Azure DevOps pipeline and AI-supported development with Claude Code CLI. Ensuring maintenance cycles. Liferay · OSGI · React · TypeScript · Azure DevOps · OIDC · Claude Code · 2026.Q1
Skills: Java 17/21, CDI, React, JSF, T-SQL, PrimeFaces, OmniFaces, Shell Script, OSGI, Felix, REST, OpenAPI, GraphQL, Python, TDD, unit tests, Clean Code, Docker, Quarkus, SQL, SMTP, WSDL, DevOps, XML, Bourne-again shell, bash, Z shell
Products used: IntelliJ, WildFly, Linux, CSS3, Docker, Elastic Search, Spring Core, Kubernetes, Argo CD, Git, GitHub, Azure, Apache Lucene, Docker Compose, Camunda, OSGI, MS SQL Server, REST, HTML5, JavaScript, OpenAPI 3, Spring, Spring Batch, Liferay, Azure DevOps, ELK, Kibana, Ehcache, SonarQube, SSL, ConfigSeeder, Bash, Shell Script
Senior Developer
SIX
Role: Senior Developer, supporting other developers
Senior Developer: Refactoring legacy Java code from EJB to REST microservices for better scalability and maintainability.
Senior Developer / DevOps: Maintenance and design of Spring Boot and Docker components to bring failover resilience to a cluster using a blue-green pattern.
Senior Developer: Converting a single persistence layer into a multi-persistence layer in legacy code. Performing integration tests and verification levels for transaction safety across all layers. Designing rollback scenarios to ensure transaction safety.
Senior Developer: Design and build of persistence layers for search indexes using Elasticsearch and modeling performance search indexes to enable search in a NoSQL DB where none existed before. Data synchronization from NoSQL to Elasticsearch – implementation of a performance-optimized search: increased response speed by >500%.
Senior Developer: Monitoring and guiding new developers (mostly external) on code quality and verifying requirements against the code.
Senior Developer: Performance optimization and refactoring of legacy Spring Batch code (production and testing) to improve speed and maintainability.
Senior Developer: Solving the generic financial product issue – implementation of a generic UX component in TypeScript and React.
Development / DevOps: Release management – rolling out new components using Docker and Kubernetes.
Skills: Scrum, Design Patterns, Java API, REST Services, Clean Code, DevOps, TDD, Lucene, SQL, PL/SQL
Products used: JetBrains IntelliJ IDEA, Docker, Docker Compose, Jenkins, CI/CD, Oracle, OracleNoSQL, MySQL 5, JPA, Mockito, ReactJS, JSON, Enterprise Architect, Confluence, JIRA, Bitbucket, Git, FindBugs, SonarQube, WSDL, REST
Lead Developer
Employment Agency
- Lead Developer: Implementation of a content and metadata search based on microservices, Angular (frontend) as well as Elasticsearch and Lucene index. Implementation with Java 8 / Spring. Modeling of search indexes with analyzers and non-persistent fields.
- Development: Frontend and backend.
- Architecture: Setup of Docker cluster and operations, DC/OS Mesos for orchestration and scaling of the microservice components.
Skills: Scrum, Clean Code, TDD
Products used: Eclipse, IntelliJ IDEA, Elastic Search, Storm Crawler, bash, Docker, DCOS Mesos, Webstorm, Spring 4.1, Apache Lucene, Spring Boot, FeignClient, OkHttp Client, Mockito, MockMvc, Bash Shell, DesignPatterns, AngularJS, JIRA, Confluence, Git, Java API, REST Services, REST, FindBugs, Angular, Kotlin
J2EE Software Developer / Architect
Energy group (Switzerland)
Development and quality control as well as code reviews of software deliveries. Setup of Continuous Delivery using JBoss RHQ. Splitting delivery packages into microservice-ready building blocks. Coupling control, guidance and regulation systems in the power sector. Bug fixes (backend J2EE, Spring, frontend JSF/PrimeFaces, AngularJS). Migration of several projects from JDK 7 to JDK 8.
- Development: Coupling different systems through data synchronization backend/frontend.
- Development: Archive data transfer to the e-archive.
- Development: Business Object Registry for the object cardinality of the different systems.
- Development: Bug fixing, integration tests, unit tests.
- Architecture: Replacing Apache Camel project with Camunda BPMN, increasing maintainability and process visibility.
- Development: Extending existing projects with Kerberos authentication service.
- DevOps: JBoss template setup with Docker and Vagrant.
Skills: Scrum, Agile, Reengineering, DevOps
Products used: OData, JSF, PrimeFaces, AngularJS, Java 8, Camunda BPM, Spring 3.0, Spring Batch, Spring Data, Feign REST Client, Quartz Scheduler, JBoss, WildFly, Git, ElasticSearch, Apache Lucene, Spring Boot, SonarQube, J2EE, JPA, JAXB, Oracle, H2, CSS, Kotlin
Developer / Team Lead (Backend/GUI)
Bank UniCredit
Team Lead: Implementation of an interface for matching master data in the area of group partners, clients, partners and group associations (debt reporting to the Bundesbank).
Tools: JBOSS 6.3 GA, Java 7, Eclipse, EJB 6, JPA, Mockito, JUnit, CDI, Jenkins, HTML, CSS, Hibernate, PrimeFaces 5.2, JSF 2.2, Activiti BPMN Engine, Apache Lucene, Batch JSR 352, JAX-WS, JAXP, REST, SOAP, Apache ActiveMQ, SonarQube, FindBugs, Maven, PowerMock, XStream
Skills: Scrum, TDD, Agile development, change request management
Products used: Atlassian Confluence, JBoss, Java 7, J2EE, JPA, Mockito, CDI, HTML5, Hibernate, PrimeFaces, JSF, Activiti, SOAP, SoapUI, JAXB, JUnit, PowerMock, Apache Lucene, SonarQube, WSDL, ActiveMQ, BPMN, FindBugs, Kotlin, Spring Batch
Head of Cytology Systems Software
amedes Medizinische Dienstleistungen
- Team size / customers: 8 people / 20 company-owned labs / 60 competitor labs outside the company
After the takeover of a lab software solution, the amedes lab services group needed someone who could move the software to a new architecture, ensure operations incl. the software certification required in Germany (every 2 years), and reassure the competing companies that no data would leave the department. The goal was smooth continued operation. After this period, the software was sold with profit to a software company.
- Management: Disciplinary responsibility for a team of software developers: employee leadership, target agreements, performance reviews, and career development of team members.
- Management: Project responsibility: planning, controlling, and monitoring software projects regarding deadlines, quality, and resource use.
- Management: Budget and cost control: total budget 2 million (staff and hardware) – creating and monitoring project budgets, resource and effort calculations, and coordination with management.
- Management: Rollout of the software to all labs (MOLIS and cytology) without interrupting operations – incl. planning, training, and briefing of the lab doctors and lab assistants who were taken over.
- Management: Leadership and coordination through a steering committee with doctors and labs for requirements gathering, project implementation, and acceptance after the business takeover by the amedes group.
- Architecture: Decision-maker and responsible for software strategy, hardware, and architecture (software and hardware).
- Organization: Responsible for introduction and operation incl. KBV certification of the software as well as quarterly billing to the KBV nationwide for about 80 labs.
Used products: MS-Project, Omnis7, Oracle 10g, PostgreSQL
J2EE Software Developer / Team Lead / Test-Driven Development
Shipping company (international project)
- Team size: 6 people
Goal: Implement a logistics application – replacing 60 isolated solutions. Project language: English (meetings, specifications, negotiations, near-shore teams). Create/design frontend in JSF and service layer/backend J2EE as well as batch processing in the area of tariff management and central systems. Process modeling with Activiti in different modules. Responsible for implementing workflow processes and requirements analysis. Distributed application for about 2,500 users in cluster operation, sync processes, async processes, batch process management, performance analysis and optimization.
Knowledge: TDD, Scrum, Clean Code
Used products: Eclipse, Icefaces, TIBCO, ActiveMQ, Gradle, Git, Jenkins, Maven, Activiti BPMN, Camunda, XSLT, XML, AltovaXMLSpy, CDI, JSF, JSFUnit, JasperReport, Mockito, PowerMock, EclipseLink, Hibernate, JUnit, Oracle 11, JPA
Project Manager / Deputy Head of Development with personnel responsibility
HHLA Hamburg Port Consulting
- Team size: 7 people
Support of an existing ERP software in the Port of Hamburg and 4 other terminals in Poland (order volume ~800,000 € p.a.). Building and standardizing missing system communication. Creating a web portal for online orders and container tracking. Negotiation and completion of SLA and migration project with the customer. Started at the beginning of the project as a freelance employee, then taken on as a permanent employee.
Used products: Java, JSF, JBoss Portal 2.7/JBoss 5, Maven, Uniface 8.3.4, JMS, J2EE, EJB3, Swing GUI, JUnit, SQL, PL/SQL, XML, XSLT, Hibernate, Spring, Subversion, Eclipse
Technology Consultant and Developer
Municipal Data Processing
- History tracking: certification-compliant change log for all software products – traceable display of data changes (incl. n:m relationships) for non-IT users.
- Journal tracking: company-wide and product-wide journal tracking based on history tracking.
- Jasper report integration: connection of the open-source reporting tool to UNIFACE (4GL call-out) via JNI through C++ to Java.
- Order dialog: replacement of a native GUI with a web GUI (multi-tier architecture with web service and loose coupling).
Used products: Microsoft Visual Studio 2005, UNIFACE 8, Eclipse, Subversion, Enterprise Architect, Oracle, SQL Server, C++, PL/SQL, TSQL, JSP, JSF, JBoss, J2EE, EJB2, Tomcat 5, Maven 2, Java 6, JNI, JMS, JUnit
Developer, Technology Consultant
Laboratory Services
Developer: Creation of a C# software to monitor lab orders by urgency and priority (layout based on information board/airport principle).
- Implementation of an in-house data warehouse reporting tool: DB export to Excel via XML and C#
- High-performance image server/client: display of scanned orders (TIFF, multi-page) in remote desktop operation via WCF/socket connection
Used products: C# frontend/backend, Sockets, Services, PL/SQL, Microsoft Visual Studio 2005, SQL Server, WCF, .NET, ADO.NET (part-time project)
Analyst and Implementer
DevOps: Migration of a compute node in the data center from an HPUX cluster to multiple nodes with openSUSE Enterprise Edition. Analysis and migration of ~36,000 Java batch and 3-tier classes (Swing + Web). Setup of test environment, mass tests, and feasibility analyses. Integration into production plan without visible interruption to the outside.
Products used: C, C++, MFC, JNLP, JNI, bash, kshell, Java, J2EE, EJB2, Swing GUI, JBoss 4, make, SQL, TSQL, XML, XSLT, ANT, Maven, Subversion
Developer, Team Lead
Logistics (Hamburg / Frankfurt)
Developer/Team Lead: New project at the client – development in Uniface for container transport in Germany. Communication with various external systems. Project size: ~15 people + the client’s IT department. Team lead for: sales conditions, web connection for external partners, web price information system, customer billing, quotations, complaints handling. Connection of external road and rail systems via web service.
Products used: Uniface 8.4.x, Java, EJB, JUnit, JSP, Servlet, Tomcat 5.x, XML, DTD, XSL, SQL Oracle, JNDI, UML, JMS, WSDL, C++, UNIFACE Application Server, Scriptura, Eclipse, XMLSpy, Oracle 9.x
Industry Experience
See where this freelancer has spent most of their professional time.
Experienced in Information Technology, Banking and Finance, Transportation, Insurance, Healthcare, and Government and Administration.
Business Area Experience
See which departments and functions this freelancer has contributed to most.
Experienced in Information Technology, Product Development, Finance, Project Management, Quality Assurance, and Operations.
Skills
Java
Architecture
Pl
Frameworks / Middleware: Spring Boot, Spring Batch, Quarkus, J2ee/Ejb, Cdi, Osgi, Jsf/Primefaces, Icefaces, Activiti Bpmn, Camunda, Apache Camel, Hibernate, Jpa, Openapi, Graphql
Frontend: React, Angular, Typescript, Jsf, Html5, Css3, Freemarker, Gwt
Search & Data: Elasticsearch, Apache Lucene, Kafka, Activemq, Tibco, Jdbc, Odata
Devops / Cloud: Docker, Kubernetes, Argo Cd, Azure Devops, Jenkins, Github, Git, Sonarqube, Shell Script
Databases: Oracle, Postgresql, Mysql, Ms Sql Server, H2, Oraclenosql
Programming Languages: Java 8/17/21 (+++), Kotlin, Typescript, Python, C++, C#, Bash/Kshell
Operating Systems: Linux, Macos, Unix, Windows
Methods: Scrum +++, Tdd +++, Clean Code ++, Design Patterns ++, Domain-Driven Design +, Pair Programming
Version Control: Git +++, Subversion ++, Clearcase ++
Application Server: Jboss 4/5/6/7 +++, Wildfly 10 +++, Glassfish 4 ++, Apache Tomcat +++
Test Frameworks: Junit +++, Mockito +++, Mockmvc +++, Powermock +, Arquillian +++
Build Tools: Maven Incl. Nexus +++, Gradle +, Ant ++
Mobile: Android ++, Ios ++
Ai / Automation: Claude Code Cli, Ai-Assisted Development, Agentic Ai Squad
Languages
Education
University of Applied Sciences for Business
Diploma in Business Informatics · Business Informatics · Paderborn, Germany
University of Applied Sciences for Computer Science
Computer Science Assistant · Computer Science
Statistics
Experience
Global Experience
Expertise
Qualifications
Profile
Frequently asked questions
Have questions? Find more information here.
Average rates for similar positions
Rates are based on recent contracts and do not include FRATCH margin.
Similar Freelancers
Discover other experts with similar qualifications and experience
Sercan Tatar
Enis Spahi
Hüseyin Korkut
Csaba Kéri
Christoph Bewerbung
Shamaila Mahmood
Stefan Amann
Stephan Giuliari
Thomas Hoefkens
Niko Schmuck
Experts recently working on similar projects
Freelancers with hands-on experience in comparable project as a Fullstack Developer
Sercan Tatar
Enis Spahi
Csaba Kéri
Stefan Amann
Sebastian Kanzow
Kiriakos Krastillis
Dirk Bolte
Shamaila Mahmood
Thomas Hoefkens
Stephan Giuliari
Nearby freelancers
Professionals working in or nearby Dübendorf, Switzerland
Susann Pataki
Gwang Jin Kim
Peter Wydler
Marco Skulschus
Nikita Verkhoshintcev
Paul Flato
Georgios Sfakianakis
Monika Elsen
Marc Pedri
Lukas Döppler
Most recent projects
FRATCH works with many companies and recruitment agencies. Here you will find our recently posted projects and opportunities.
