Java SE/EE, Kotlin, Scala, Groovy, RxJava, Spring Framework (Core, Data, Boot, Batch, Cloud, Security, Retry, MVC, AOP, Reactor), MapStruct, Lombok, Feign, WebFlux, Vert.x, jOOQ, Hibernate, JPA2, QueryDSL, Kafka, RabbitMQ, ActiveMQ, IBM MQ, Apache Spark, Apache NiFi, Apache Camel, Flyway, Liquibase, Keycloak, Microservices Architecture, ELK, Prometheus, Grafana, Splunk, AppDynamics, Docker, Kubernetes, OpenShift, REST, WebSockets, RSocket, SOAP, GraphQL, GWT, DB (Oracle, PostgreSQL, MySQL, MongoDB, Cassandra), Lucene, Solr, ElasticSearch, Redis, Ehcache, Hazelcast, Caffeine, Camunda, Activiti, Zeebe, jBPM, Flowable, JUnit, TestNG, Mockito, Cucumber