Full Stack Software Engineer

Russian hacker, Vladimir Leonidovitch Levin, attempted the biggest bank heist the world had ever seen via dial-up internet in 1994, Zia Hayat, Callsign CEO and founder, was hooked - armchair fraud became a real possibility. From this moment, Zia knew he wanted to play a part in stopping the bad guys and securing the internet for all. Founded In 2012, Callsign's mission has been to make Digital Identity simple and secure for everyone and everything. In that time, we've grown to over 250 employees, opened offices in UK and Abu Dhabi, been recognised as a WEF Global Innovator and our technology is being used by many of the world's leading financial institutions to keep millions of consumers safe. But we aren't stopping here. The identity revolution has only just begun, and we are looking to hire the brightest and inquisitive minds to help us make every web, mobile and physical Interaction seamless and secure. If this sounds like you, lets chat. As a Full Stack Software Engineer at Callsign, you will design, build, and maintain end-to-end features spanning our high-throughput Java backend services and modern web interfaces. You'll work in an Agile, collaborative environment alongside Product, UX/UI Designers, and QA to deliver secure, scalable, and intuitive digital experiences. You will take ownership of features from architectural design through implementation, testing, deployment, and operational monitoring. Design, build, and maintain scalable Java-based backend services and modern frontend web applicationsDevelop robust RESTful APIs and integrate frontend interfaces seamlessly with backend systemsBuild responsive, accessible, and performant user interfaces using modern web frameworksWrite clean, testable, and maintainable code across the full stack following engineering best practicesCollaborate closely with Product Managers, UX/UI Designers, QA, and platform teams to translate user requirements into technical solutionsParticipate in peer code reviews, contribute to architectural discussions, and proactively address technical debtSupport deployment pipelines, troubleshoot production issues across frontend and backend layers, and drive continuous improvement Requirements 3-6 years of commercial full-stack software development experienceStrong backend expertise in Java, Spring Boot, and RESTful API design; gRPC experience is a plusHands-on frontend experience with modern JavaScript or TypeScript frameworks, preferably React. Commercial experience with Vue.js or Angular is also welcomeProficiency in JavaScript, HTML5, CSS3/SCSS, and responsive UI designWorking knowledge of frontend build tools and package managers such as Vite, Webpack, npm, or yarnSolid experience with relational databases such as MySQL, PostgreSQL, or Oracle, and SQL query writingStrong understanding of OOP fundamentals, SOLID principles, and data structures and algorithmsFamiliarity with testing frameworks across the stack, such as JUnit, Mockito, Jest, React Testing Library, or CypressFamiliarity with Docker, Linux environments, and CI/CD pipelinesExposure to microservices architectureAwareness of secure coding practices including OWASP Top 10, XSS, CSRF prevention, and secure authentication/token managementStrong communication, analytical thinking, and collaboration skills Good to have : Experience with Java 17 and Spring WebFlux with Project Reactor, or Java 21+ Virtual ThreadsProduction experience with NoSQL systems such as DynamoDBProduction experience with TypeScript and modern frontend state management such as Redux Toolkit or ZustandFamiliarity with design systems, component libraries, and tools like Storybook or FigmaProduction experience with microservices architecture, distributed caching with Redis, and event streaming with KafkaFamiliarity with container orchestration, Kubernetes, Helm, and cloud platforms such as AWS or GCPFamiliarity with observability and monitoring tools such as Prometheus, Grafana, OpenTelemetry, or Elastic StackBasic understanding of web accessibility and web performance optimisation Benefits Private Premium Health InsuranceVisa costs including 1 month paid hotel stay on arrivalAnnual Airfare Allowance for the home country3 months full pay maternity leaves & 2 weeks full pay paternity leaves25 days of annual leave + Callsign Bank Holiday (not included in holiday allowance)Competitive SalaryGratuity as EOSB