Senior Software Engineer - Backend - Core at five9

This role is designed for a seasoned Java specialist with at least 8 years of professional experience who thrives on building mission-critical, high-scale backend infrastructure. The ideal candidate has a deep mastery of the Spring Framework and distributed systems, with the technical maturity to take end-to-end ownership of core platform services that other engineering teams will rely on. This is a high-visibility position based in Porto with a hybrid work structure. While the base salary isn't listed, the package is robust, including company shares, a bonus scheme, and a "10% Flexi Benefit." The role offers the chance to influence architectural standards across the entire organization, making it a great fit for someone who wants their code to serve as the "gold standard" for scalability and performance. **You might be a good fit if you...** * Have 4+ years of dedicated Java backend experience and a "pro" level understanding of multithreading. * Are comfortable with on-call rotations and troubleshooting complex production issues in a distributed cloud environment. * Enjoy designing RESTful/RPC interfaces and working with event-driven architectures. * Possess strong Computer Science fundamentals, particularly in data structures and complexity analysis.