Senior Software Engineer: 3DS Payments

Why Keystone AI Founded over 16 years ago, with more recent investments from Accel-KKR, Keystone AI is a leader in digital banking fraud prevention and payment security, including mobile authentication, mobile app security, and 3D Secure authentication for issuers, acquirers and payment networks. We offer highly scalable products with a track record of success across multiple continents. Keystone AI enables secure digital transactions for leading financial institutions globally. We exist to create a world where everyone can transact digitally without fear or compromise. Currently, we protect the digital transactions of over 210 million active users on our platform and hold 120 active patents that recognize innovation in digital security, payments, and user experience. Keystone AI offers customers secure authentication and digital payments experiences that remove unnecessary friction. Keystone AI has a diverse product portfolio and aggressive roadmap that positions the company well to sustain competitive advantage as it expands globally with emphasis on North America and European markets. The Ideal Candidate The ideal candidate is a senior backend engineer with strong Java expertise who is comfortable working on security‑critical, regulated systems. You have experience designing, building and maintaining distributed backend services, enjoy taking ownership of complex technical problems, and are able to balance delivery with long‑term maintainability. You are confident working independently, contributing to architectural decisions, and mentoring other engineers, while collaborating closely with product, QA and DevOps teams. Experience in payments, fintech or other high‑security environments will be a strong advantage. The Role As a Senior Software Engineer in the 3DS Payments team, you will work on backend services that support secure payment authentication and the handling of sensitive data. The role focuses on developing and maintaining Java‑based services, improving system reliability and performance, and ensuring compliance with security and regulatory requirements. You will contribute to system design, guide technical decision‑making, and help drive continuous improvement across the codebase and platform. Responsibilities Design, develop and maintain backend services within the 3DS Payment’s platform Build and maintain RESTful APIs and distributed systems Develop and support Java applications deployed on Apache Tomcat Design, optimise and maintain MySQL database schemas and queries Identify and resolve performance, stability and production issues Contribute to architectural decisions and technical tradeoffs Ensure systems adhere to secure coding practices and compliance requirements Collaborate with product, QA and DevOps teams throughout the delivery lifecycle Mentor and support other engineers within the team Take ownership of features and services from design through to production Skills and Experience Successful candidates for this role will generally possess the following qualifications and skills: 5 - 8+ years of professional software engineering experience with strong proficiency in Java (Java 11+ required; newer LTS versions a plus). Experience developing applications running on Apache Tomcat. Solid experience with MySQL or similar relational databases, including: Schema design Query optimisation and indexing Performance tuning and troubleshooting Experience building RESTful APIs and working with distributed systems. Strong understanding of software design principles (OOP, SOLID, clean architecture). Experience using Git or similar version control systems. Strong understanding of secure coding practices, including OWASP Top 10. Experience working in regulated environments (e.g. PCI DSS, GDPR). Experience handling sensitive data such as cardholder data or PII. Nice‑to‑have: Experience with AWS (EC2, RDS, S3, IAM, CloudWatch) Exposure to cloud‑native or cloud‑migrated architectures Experience with Docker and/or Kubernetes Familiarity with CI/CD pipelines and DevOps practices Experience in payments, fintech or other high‑security domains Personality Attributes Strong problem‑solving and analytical thinking skills. Clear and effective communicator with both technical and non‑technical stakeholders. Comfortable working independently and taking ownership. Collaborative team player with a pragmatic, delivery‑focused mindset. Strong attention to quality, security and maintainability. We place a lot of value on how we treat prospective employees and appreciate the time and effort that goes into job hunting. That is why we aim to keep the hiring process as quick and seamless as possible while ensuring the best possible fit for both you and the company. Working at Keystone AI is truly a dream. You get exposed to cutting-edge technology, colleagues who are leaders in their fields, and an awesome working environment that includes flexible hours, remote work, and plenty of growth opportunities. Apply for this position by