Savas Duvan

Providing medical care to my mother

As a subcontractor within the CapGemini Tracces Agile team, I have co-worked with UX/UI designers, product owner, front-end, back-end developers and testers.

I have contributed to the following:

• Design and development of microservices utilizing Java (17/21), Spring Boot (3.5), Spring MVC, Spring Data JPA / Hibernate, Spring Security, Redis, RabbitMQ,
• Design and development of REST APIs applying Contract-first design, Fail-fast principe, API Design Best Practices, and utilizing Open API, Swagger,
• Deploying of applications to Kubernetes utilizing Helm, Gitlab CI/CD-pipelines,
• Developing of custom metrics for KPIs (Micrometer, Splunk, Prometheus),
• Developing Unit and Integratie tests (JUnit, Mockito, TestContainers),
• Developing PoCs, MVPs and holding demos during Sprint reviews and to back-end team peers,
• Developing of a foundation for the API Test Automatization suite (Postman, GitLab),
• Conducting impact analysis and performing the Java migration 17 -> 21, Spring Boot migration 3.2 -> 3.5,
• Conducting peer code reviews,
• Participating in weekly knowledge sharing sessions ,
• Participating in Hackathons, PI Planning events,
• Participating in Scrum ceremonies (Daily, Retro, Review, Planning),
• Writing technical documentation (Confluence).

Developing and transferring Java services to a private cloud, within a SOA-oriented landscape of the CJIB, with a focus on Agile/DevOps methods:

• Using Java/J2EE, JPA (EclipseLink), JMS (HornetQ), JTA (Atomikos), Database (Postgres), Spring Boot, Spring WebServices, Spring Data, Spring MVC, Maven, Jetty, Linux and supporting tools such as Jira, Confluence, Bamboo,
• Cloud-ready development (Service Discovery, Spring Cloud),
• Testing developed services with automated test frameworks such as Citrus, Protractor, JMeter,
• Monitoring (Splunk, Kibana, Grafana), profiling, tuning a service,
• Conducting peer code-reviews,
• Collaborating within an Agile/Scrum team.

Senior Java developer at International Payments area. I am responsible for shaping the technical vision of the microservices with the Java Chapter and Chapter Lead.

I operate according to an Agile Scrum development process and strongly believe in the DevOps approach to delivering IT solutions. My focus is on high-quality software delivered continuously using iterative development. I strive to deliver working software every 2 weeks to production.

My responsibilities:

• Developing and maintaining microservices handling system integrations (Java 11/17, Spring Boot, Spring Integration Java DSL, Jakarta EE JTA, Kafka, Tibco, Active MQ, XML/XSL, JPA / Hibernate, Azure DevOps, Oracle, Maven)
• Working on development,  integration, implementation and deployment of APIs. (Spring Web MVC, TDD)
• Participating in Scrum ceremonies; daily stand-up, planning, refinement, retro. Improving the Way-of-Working (WoW)
• Code collaboration via code reviews (Git, Azure DevOps)
• Participating in production support during incidents.
• Active contributor within the Java Chapter (CoE) by developing and presenting PoCs.

As a member of the Nike ED&A (Enterprise Data & Analytics) domain, I have acted as a Lead / Senior Java Developer within the UMD (User-Managed Data) squad (6 FTE). My contributions started with the re-design of the UMD application.

UMD, leveraged by Nike globally, empowers business users to manage their own data structures and inject these into Nike's Data & Analytics space.

Some of the activities I have performed are:

• API-first approach by designing the bounded-contexts, business domain, collections and resources  (Springfox, Open API v3)
• Design and implementation of the layers of the composite and core microservices (Java 8/11, Spring Cloud, Gateway, Resilience4J, Distributed Tracing)
• Implementation of a event publisher/producer (Spring Boot, Apache Kafka)
• Implementation of reactive data repositories, API's, services and controllers (Spring Mongo Reactive, WebFlux, Reactor, Spring Data JPA)
• Implementing an RBAC (Role-Based Access Control) model and security for the end-points with a custom permission evaluator (oAuth2 Resource Server, Spring Security)
• The below PoCs were conducted and presented to the architecture board:
  • Implemented a data pipeline for streaming data from AWS Postgres to Snowflake with Spring Cloud Data Flow (SCDF) by extending the JDBC source application.
  • Implemented a batch component to satisfy the above requirement to improve performance and data consistency. (Spring Batch and Scheduling)
  • Implemented an LDAP component to lookup members from a given AD group (Spring Data LDAP)
• TDD: Developed unit and integration tests throughout all the layers (Mockito, Reactor Test)
• CI/CD: Containerization of microservices, with having best practices in mind, and deployment to EKS cluster (Docker, Kubernetes, Helm, Jenkins)
• Participating in Scrum Planning, Review/Demo, Retrospective and Refinement sessions.
• Providing x-training sessions to squad members (dedicated day each sprint)
• Technical interview of new candidates

Following, I joined the Pathfinder team (12 FTE) and delivered the following:

• Development of a custom Kubernetes admission controller (fabric8io/kubernetes-client)
• Refactoring the custom security model of the Java-based APIs to utilize Spring Security code infrastructure.
• Implementing an internal gateway that delegates the request to another central component which then receives the URI to proxy.
• Improving test coverage of the APIs by adding MVC tests.
• Implement/exposing actuator metrics to Prometheus which are visualized in Grafana.
• Maintain the IaC (Terraform) scripts.
• Participating and contributing to CoP (Chapter of Practice) Fullstack. (0.2 FTE)
• Conducted and presented the below PoC's within the scope of Spike stories:

  • Developed a Proof of Concept to perform ETL processing in order to setup a foundational component to decommission a legacy component based on NodeJS and Excel (macros).

    I have provided and presented a component design with a target achitecture being a microservice hosted on AWS, with Kubernetes as deployment runtime.

    This component, a Spark job entailed loading data from Spark RDD, performing data transformations (custom mappings), enriching the data, and writing to Kafka.
    Also I have used the Spring Boot Actuator and Micrometer dependencies in order to expose out-of-the-box and custom metrics so that these were presented in Grafana in the next sprint cycle.
     I have used Java 11, Spring Boot 2.5, Kafka (Spring Boot abstraction types KafkaTemplate, @KafkaListener, KafkaTransactionManager), Spark Java (JavaSparkContext, JavaRDD), Docker and Helm as the Kubernetes package manager. 

  • Jenkins service: provide real-time Jenkins job triggering and status for simple pipeline management (Spring Boot, Jenkins API)
  • Serverless functions: demonstrate a set of functions in order to benefit from the serverless stack (Spring Cloud Function, AWS Lambda, AWS API Gateway)
  • Notification Service: real-time feedback to end-users providing Pub/Sub endpoints (AWS SNS, Spring Boot, Spring Cloud AWS)

Phase 2 of previously launched e-Recruiter in Q1.2018 aiming to provide both
functional, technical and infrastructural enhancements according to the product
roadmap:

• Decoupling of microservices by Pub/Sub async messaging for 3rd party
  integrations (Spring Boot, RabbitMQ, Spring Cloud Stream)
• Converting all MVC based REST controllers to being non-blocking I/O (Java 11, Spring WebFlux/Project Reactor)
• Migrated Netflix components such as Hystrix, Ribbon, Zuul to respectively
  Resilience4j, Spring Cloud Load Balancer, and Spring Cloud Gateway.
• Asynchronous distributed tracing to decrease load and runtime dependencies of
  the microservice landscape (Spring Cloud Sleuth, Istio Kiali/Jaeger, RabbitMQ)
• Setting up centralized logging and custom charts within a separate Kubernetes
  namespace. (ElasticSearch, FluentD, Kibana - EFK stack)
• Setup custom application monitoring and alerting for Circuit Breakers and Retries
  running in Istio Service Mesh (Actuators, Micrometer, Prometheus and Grafana)
• Migrated containers from AWS EC2 to Amazon EKS cluster with Istio Service Mesh
  in order to improve observability, security, and reliability
• Development of Candidate Job Dashboard and Search modules (Angular, Angular
  Material)
• TDD - Conducted PoC on producer- and consumer-driven contract testing (Spring
  Cloud Contract)
• Moving API landscape documentation for increasing agility and maintainability
  (SwaggerHub)
• Documentation of new procedures, run-books, release templates.

Within the "Distribution / Relevance Insight and Sales (RIS)" domain of Rabobank Cooperative Banking, I act as a DevOps / T-Shaped developer to contribute to on-going projects.

An outline of the tasks I have been performing:

• Front-, backend development and maintenance of Corporate banking widgets. (AngularJS, Java 8, Spring Boot, Oracle) 
• Developing Unit, Integration and Live API tests (DBUnit, JUnit, Mockito, RestAssured)
• Developed a containerized subscriber (consumer) to process events from the Business Event Bus and persisting to the database (Spring Boot, Kafka, Actuators, Oracle, Docker)
• Setup and configure CI/CD pipelines (Jenkins)
  
• Conducted Proof-of-Concept and event sourcing during the first milestones of the cloud transformation pilot (Pivotal Cloud Foundry-PCF, CloudAMQP, ElephantSQL)
  
• Monitoring and troubleshooting (RCA) applications
• Collaborating with other project teams, participating in Scrum plannings and retrospectives, conducting demos to stakeholders
• Conducting peer code reviews, performing technical documentation

Transformation of a monolith into a microservice landscape, e-Recruiter is the new platform of Kelly Services to be launched in Q1 2018.

e-Recruiter covers and implements the Cloud design patterns / best-practices aligned with the 12-factor methodology.

• Functional decomposition of the business domain into microservices, establishing service granularity, defining the service interfaces (API-first design, DDD)
• Setup a Spring Cloud Config server that is deployed as Docker container and can be managed as the core configuration of all the microservices.
• Setup an Eureka server running as a Spring-Cloud based service. This service will allow multiple service instances to information using a file system or GitHub-based repository.
• Development of a service gateway with Zuul API so that all microservices can be routed through the gateway and service, register with it. Clients that need to call a service will use Eureka to lookup the physical location of the target.
• Setup an Apache Kafka message bus to transport messages between services, have pre-, response- and post policies enforced on the calls
• Setup and implement distributed caching via REDIS
• Setting up a cloud topology with Amazon (AWS) EC2 clusters, Docker containers, REDIS distributed cache, PostgreSQL and Load Balancers
• Setting up CI/CD pipelines, notifications with GIT and Travis-CI
• Setting up distributed logging, tracing and visualization with OpenZipkin
• Sprint planning and weekly technical management of 4 offshore (3 DEV + 1 QA) resources based in Hyderabad, India
• Perform Technical and end-user documentation

I have managed an off-shore team to deliver a custom product, e-Builder; a SPA (Single Page Application) targeted for construction builders to manage the entire life-cycle of construction projects. I was involved in the architecture, design, and development during the entire SDLC.
My responsibilities were:

• Daily technical management of 12 offshore resources (DEV and QA) based in Hyderabad India
• Requirements analysis, risk-workshops, providing estimations and work break-down
• Setup application architecture (microservices), design and the AWS topologies (REST API's and data layer managed through the AWS Cloud)
• Design, develop and test (TDD) a multi-tier reference implementation and handover to the development team
• Defining and setting up Docker images, containers and repositories
• Review design and code, review and fix tests and functional coverage
• Setting up a Continuous Integration and Delivery (CI/CD) pipelines
• Conduct delivery and handover activities to the client

I contributed to Canon's web transformation program having as a business goal to re-design the public website into a new portal/web content management platform (IBM Portal/WCM) along with re-designing the custom integrations.

My main deliverables were:

• Requirements analysis, estimations with the teams
• Developing Java components for WCI (Web Content Integrator)
• JSR Portlet development
• WCM custom component development
• WCM custom rendering plugin development
• Developing WCM authoring and presentation templates
• Performing technical documentation and conducting hand-over sessions

I have contributed to the development and technical maintenance of the intranet of H&M Inside version 1.0 and Inside “The Make-over”, version 2.0.

My responsibilities were:

• Setup, verify architecture and design of Inside
• Stakeholder presentations, requirements- and risk workshops
• Performing application design and estimation sessions with the team
• Modelling UML Use-case-, Component- and Deployment diagrams
• ERD and RDBMS modeling
• Java development, JSR Portlet development, IBM WCM (Web Content Management) component development
• Design and development of a service layer (JAX-RS) interfacing an Oracle warehouse
• Troubleshooting and support

As a developer I have been contributing during the below customer assignments:

As a developer, I have delivered in several customer-facing assignments mainly in UK. Some projects were:

• Designed and implemented a prototype printing module for a consultancy company in Denmark. This generic module provided print-functionality for a healthcare information system.
• Implemented a Self-Assessment System for Royal Mail England. The application provided extensive reporting and PDF printing functionality.

As a Java developer, I participated in many in-house projects such as:

• Maintenance of the Business Rules Engine
• Development and maintenance of Experian, Schufa interfaces
• Development of Online Consumer- and Corporate Banking projects and products
• Design and development of the e-ServiceDesk system