Ajax Systems, an international tech company and the largest manufacturer of security systems in Europe. We are looking for a new team member to join our System devisions as a Senior Java Developer. The System Division is responsible for building and developing the Ajax software ecosystem. The team develops and maintains OS Malevich and the Video Management System, builds scalable cloud infrastructure, and creates client applications for multiple platforms, ensuring that all system components work together as a unified ecosystem. The division works with Java, Kotlin, Swift, C, C++, and Python. It includes embedded, cloud, mobile, and desktop engineers who ensure the stable operation of Ajax as a single digital platform. Required Experience: * Java: 3+ years of professional backend development in enterprise environment * Kotlin: Knowledge and practical work experience * Java Concurrency: Strong understanding and practical application experience Architecture & Design: * Understanding of SOA, microservice, and event-driven architecture * Cloud development principles with practical AWS experience * Ability to scale and ensure high availability of loaded systems Technologies & Tools Required: * MongoDB, NATS * Enterprise-grade stack (messaging brokers, in-memory storages, NoSQL, key-value databases) * Docker and Kubernetes (containerized applications) * Git, Gradle, Jenkins Nice to Have: * Redis, Netty, Akka, gRPC, Project Reactor We offer: * The opportunity to suggest and implement your own ideas that directly influence the product and its mass production * A place in a fast-growing company with a motivated and professional team * Competitive salary * Medical insurance * English classes * The opportunity to participate in Ajax’s internal beta-testing program for security systems  * Discounts from partner companies * Discounts on Ajax products Ajax Systems is a Ukrainian success story that has grown into a global product. Ajax devices are trusted by more than 4.5 million end users and 330,000 PRO users in over 180 countries. The company provides comprehensive solutions to protect residential and commercial properties of all sizes. Today, Ajax portfolio includes 280 devices for intrusion protection, video surveillance, fire safety, and comfort and automation.