09/02/2026 updated
100 % available
Senior Java Backend Developer
Žilina, Slovakia
Only remote
Ing., Economic Informatics, Univ. of Žilina, Faculty of Management Science & InformaticsKeycloakJava (Programming Language)Spring SecurityMicrosoft AzureApache CXFCouchbase ServersElasticsearchHibernatePostgreSQLExtensible Stylesheet Language Transformations (XSLT)OpenapiEvent-driven ArchitectureSpring BootBackendSpring Data
Java Backend Development
14 years building enterprise Java backends — Spring Boot, Spring Security, Spring Data JPA/Hibernate, Jakarta EE, Java 17/21. Delivered for public administration, smart city and IoT platforms, consumer subscription billing and enterprise document composition.
Enterprise Document Composition & PDF Rendering
Core developer on a commercial document composition platform used by large organisations to generate contracts, invoices and statements at scale. Own the rendering engine: XSL-FO to PDF via Apache FOP, XSLT/XPath processing via Saxon. Earlier, built official state document pipelines with XSLT, XSL-FO and JasperReports.
Content Repository — Apache Jackrabbit / JCR
Designed and maintained versioned content repositories on Apache Jackrabbit (JCR/WebDAV) for template and resource storage, with full-text search across stored documents.
Event-Driven Architecture & Apache Kafka
Owned Kafka as the messaging backbone of a smart parking platform — topic and event design, producers and consumers across services. Solved exactly-once concerns over at-least-once delivery through idempotent consumers and deduplication. Data pipelines with Spring Cloud Data Flow.
API Design & Domain-Driven Design
Contract-first REST APIs documented with OpenAPI/Swagger, consumed by mobile clients, decoupled frontends and third-party integrators. DDD as the default approach to modelling services.
Mission-Critical Public Sector Systems
Built and supported the Slovak national election information system — statutory deadlines, near-zero downtime tolerance, extreme peak load on election nights — and the central Register of Legal Entities consumed across government. SOAP/REST integration via Apache CXF.
Data & Search
PostgreSQL, Oracle, Couchbase. Full-text search with Hibernate Search/Lucene and Elasticsearch.
Cloud, Containers & Security
Docker, Kubernetes on Microsoft Azure. Keycloak (OAuth2/OIDC) as central identity layer. Camunda BPM for process orchestration.
Platform Modernisation
Java and Jakarta EE migrations, Spring Boot upgrades, security vulnerability remediation, multiple parallel release branches in simultaneous production use.
Experience
Professional experience10+ years
Freelancer since2023
Languages
EnglishGoodSlovakNative speaker
Project history
Backend developer on an enterprise document composition platform used by large organisations to design, generate and archive customer-facing documents at scale — contracts, invoices, statements, correspondence.
Own the rendering and composition engine: XSL-FO to PDF via Apache FOP, XSLT/XPath processing via Saxon. Also own the Apache Jackrabbit (JCR/WebDAV) content repository for versioned template and resource storage, and the REST APIs consumed by all frontends. Ongoing responsibility for platform modernisation (Java and Jakarta EE migrations, Spring Boot upgrades), security vulnerability remediation, and maintaining several parallel release branches in simultaneous production use by different customers.
Designed and built Workplace 2.0 from scratch — data model, REST API and security layer — with full-text search via Hibernate Search/Lucene and real-time updates over WebSocket. Contributed backend groundwork for an AI-assisted template editing feature on the OpenAI API.
Technologies: Java 17/21, Spring Boot, Spring Security, Spring Data JPA/Hibernate, Apache FOP, Saxon, Apache Jackrabbit, Apache Kafka, PostgreSQL, Hibernate Search/Lucene, WebSocket, REST, OpenAPI/Swagger
Backend developer on the subscription, licensing and billing platform for a consumer security product with a global user base, covering the licence lifecycle from purchase through renewal.
Owned the ordering and price calculation domain — resolving which product tiers a customer had ordered and computing the resulting price. Built as event-driven Spring Boot microservices with Apache Kafka for asynchronous order and licence event processing, PostgreSQL as primary datastore and Elasticsearch for search. External dependencies stubbed with WireMock so pricing scenarios ran reliably in CI.
Technologies: Spring Boot, Apache Kafka, PostgreSQL, Docker, Elasticsearch, WireMock
Backend developer on ParkDots (parkdots.com), a cloud-hosted smart parking platform for municipalities and private operators: mobile parking sessions, permit-based parking, sensor occupancy data, enforcement workflows and payment gateway integrations.
Owned Apache Kafka as the messaging backbone — event and topic design, producers and consumers across services, and asynchronous integration between microservices. Solved exactly-once processing concerns inherent to at-least-once delivery through idempotent consumers and deduplication. Built data pipelines on Spring Cloud Data Flow.
Responsible for integrations with external and sensor-equipped parking systems, normalising heterogeneous vendor interfaces into a common event model published to Kafka. Delivered Swagger-documented REST APIs for mobile clients and third-party integrators.
Microservice architecture on Spring Boot following domain-driven design, deployed to Kubernetes on Azure, with Keycloak (OAuth2/OIDC) and Camunda BPM.
Technologies: Spring Boot, Apache Kafka, Couchbase, PostgreSQL, Docker, Kubernetes, Microsoft Azure, Spring Cloud Data Flow, Camunda BPM, Keycloak, WireMock, Swagger