Senior Java Developer (f/m/d)

Location: Hybrid (Darmstadt) or Virtual (Germany). Role Overview: We are looking for an experienced and Senior Java Developer with specialized expertise in IBM z/OS mainframe environments, especially for online applications under CICS. This role goes beyond conventional Java development — we need someone who understands how to engineer high-performance, low-latency Java applications that run natively on the z/OS platform and integrate seamlessly with legacy enterprise systems. This position requires deep knowledge of Java in the context of z/OS internals, particularly in the areas of Java Native Interface (JNI), database interaction (JDBC, SQLJ), and system-level online performance. You will work with both legacy and modern components to develop robust, high-throughput services that are critical to enterprise operations. Key Responsibilities: • Develop and optimize Java-based applications running natively on IBM z/OS in online mode under CICS • Analyze and improve performance at the JVM level, focusing on memory usage, tuning, and CPU cycles on z/OS. • Integrate Java applications with native z/OS components using JNI, C/C++, and LE (Language Environment) interfaces. • Implement efficient data access solutions using JDBC, SQLJ, and DB2 for z/OS best practices. • Collaborate closely with z/OS systems programmers, DBAs, and COBOL/CICS developers to ensure reliable and performant interoperability. • Review SMF records, RMF reports, and monitor WLM metrics to guide tuning and system integration. • Develop and maintain shell scripts and support automation for Java workloads on z/OS. • Drive initiatives to modernize legacy systems using Java and hybrid integration models. Required Qualifications: • Bachelor’s or master’s degree in computer science, Software Engineering, or a related field. • 8+ years of professional Java development experience, with 5+ years specifically on IBM z/OS. • Deep knowledge of JVM performance tuning on z/OS, including heap sizing, GC policies, zAAP/zIIP processor utilization, and WLM workload classification. • Strong proficiency with JNI for interfacing Java with COBOL/C/C++ modules. • Expertise in JDBC, SQLJ, DB2 for z/OS, and mainframe database performance tuning. • Solid hands-on experience with USS (UNIX System Services), JCL, and TSO/ISPF. • Working knowledge of LE (Language Environment) and how Java integrates with native z/OS programs. • Familiarity with SMF, RMF, SDSF, and performance analysis tools like IBM OMEGAMON, MainView, or BMC tools. What’s in it for you? • Earn competitive total compensation and receive comprehensive country-specific medical and other benefits. • Enjoy time and location flexibility with our Hybrid Working Model, which allows a remote workshare of up to 60%. Work anywhere in your country or abroad for up to 10 days per year. Set yourself up for success in your new role by upgrading your home office space using your one-time hybrid work payment. Lean on the Employee Assistance Program for support during some of life’s most common but difficult challenges. INTERESTED? We look forward to receiving your complete application documents. Your application should include a short cover letter, a CV in tabular form and your training and work references. Your contact: Archana Singh, Lead Talent Acquisition Partner * f/m/d - Diversity matters!

ZEAL Network SE is a dynamic, international group of companies that has been creating exciting and innovative lottery experiences for over 20 years. As Germany’s largest provider of online lotteries through our brands LOTTO24 and Tipp24, and a trusted partner of Spain’s ONCE, the second-largest national lottery, we’re shaping the future of the lottery industry. We are passionate about driving innovation, as demonstrated by our newest brands, Freiheit+ and Traumhausverlosung, which bring fresh and exciting dreams to life. Additionally, through ZEAL Ventures, we invest in inspiring e-commerce start-ups like Omaze and DAYMADE, fueling fresh ideas and opportunities. We are looking for a (Senior) Full Stack Next.js Developer (f/m/d) to join our team and contribute to building scalable workflows, integrating backend services and defining reusable frontend patterns for a platform used by internal colleagues across multiple markets and business domains. With direct access to users, you will help shape practical solutions together with Product and UX. YOUR TASKS: * Shape and build a modern Next.js application from scratch, creating the technical foundation for a scalable internal platform * Take ownership of frontend topics and drive technical decisions * Work closely with product, design and backend teams in a lean, agile environment * Integrate and evolve RESTful APIs in collaboration with backend engineers * Ensure high-quality implementation of UI/UX designs with a strong focus on performance and scalability * Write and maintain tests to ensure reliability, security and performance * Contribute to deployment, monitoring and overall application stability together with DevOps * Identify and drive improvements in performance, user experience and conversion * Measure, analyze and iterate on product features based on data WHAT YOU OFFER US: * Strong experience as a Senior Full Stack or Frontend Engineer with a focus on modern web technologies * Deep expertise in JavaScript, React and Next.js (App Router, Server Components, Server Functions) * Proficiency in TypeScript, HTML5 and CSS3 * Hands-on experience with tools such as Tailwind CSS, React Hook Form, TanStack Query, Zod, Shadcn/UI or similar (Tailwind CSS is a must have, everything else nice to have) * Ability to write clean, maintainable and performant code and design scalable architectures * Solid experience integrating and working with REST APIs * Experience with testing strategies for frontend applications (nice to have) * Interest in using modern development tools, including AI-assisted workflows, to improve productivity and quality (nice to have) WHAT WE OFFER * State-of-the-art technologies and an agile environment (Check our Tech Radar: https://lotto24.github.io/tech-radar/) * A modern, dynamic culture grounded in the success of a leading-edge e-commerce company. * A talented team of ambitious, like-minded colleagues where your knowledge and ideas truly make an impact. * Ongoing personal growth, supported by an annual development budget of €1,500 to invest in your professional development. * Trust and autonomy, no micromanagement, just confidence in your ability to deliver and excel. * Flexible work options with a hybrid setup focused on results. * Unlimited vacation days in addition to your yearly 30-day vacation allowance. * Opportunity for workations abroad using our WorkFlex tool. * Monthly mobility allowance of €30 to use on the mobility option of your choice (e.g., the Deutschlandticket), plus access to a company bike leasing program. * Company pension scheme, provided in partnership with Degura, to support your future financial security. * Subsidized EGYM WELLPASS membership, with a contribution of only €25 per month, giving you access to a wide range of gyms and sports options across Germany. * Monthly company events, team activities, and informal gatherings, including our popular company-wide lunches provided four days a week. Not ticking every box or think you’ve got that unique set of skills we haven’t realized we need? Get in touch anyway, we’re always looking to add great people!