Software Engineer, Java, Zalo

• Take ownership of new feature development within Zalo's authentication system — covering areas such as login, session handling, and token management — while keeping performance and scalability in check as the user base grows;
• Regularly review and improve existing authentication features to reduce latency, fix reliability issues, and make the overall experience smoother for millions of Zalo users;
• Work directly with product managers and client teams (iOS, Android, and PC/Web) to understand what needs to be built, raise technical concerns early, and deliver solutions that hold up in the long run;
• Be responsible for backend services that handle high volumes of authentication traffic every day — writing code that is production-ready, well-tested, and easy for the team to maintain;
• Set up logging and monitoring that give the product and data teams real insight into how users are interacting with Zalo's authentication services, and flag issues before they become problems;
• Keep up with developments in backend and security engineering, and bring in new tools or approaches when there is a clear benefit to the system;
• Coordinate with infrastructure teams on release processes, on-call rotations, and making sure critical services have the right level of observability in production.

• Bachelor's degree or above in Computer Science, Software Engineering, or a related field;
• At least 2 years of hands-on experience building backend services with Java and Spring Framework, with a solid understanding of OOP principles;
• Comfortable working with microservices architecture, Linux environments, and both relational and NoSQL databases. Experience with caching solutions such as Redis or Memcached is expected;
• Good understanding of common web security risks — XSS, CSRF, SQL injection, CSP — and how to build systems that account for them from the ground up.

Nice to have

• Experience designing or scaling systems that serve a large number of concurrent users — ideally in a high-traffic production environment;
• Familiarity with CI/CD workflows using Jenkins or GitLab CI, and a habit of writing automated tests as part of regular development;
• Some exposure to front-end technologies (JavaScript, React, or similar) — useful for building internal tools to support monitoring, debugging, or operational workflows;
• Able to read and communicate in English at a working level — most technical documentation and cross-team discussions are in English.