Senior Backend Developer - PHP

PayXpert is a pioneer in omnichannel payments and a subsidiary of the Société Générale group. We serve a diverse array of local and international brands both online and in-store, spanning various sectors. At the heart of our vision is the creation of a payment ecosystem that fosters an inclusive commerce experience for all.We have developed services that focus on revenue optimisation, performance enhancement, fraud prevention, and seamless payment orchestration. Our expertise extends to cross-border payments and alternative payment methods such as Alipay+ and WeChat Pay. Furthermore, our solutions are designed with accessibility in mind, offering features that cater to the visually impaired, ensuring everyone can engage in the modern commerce landscape.The Senior Backend Developer is responsible for designing, building and evolving the backend services that support PayXpert's Payment Gateway, Secure Store and other security‑sensitive components within the core payments platform.The role spans mainly on the PHP‑based e‑commerce gateway but also on the Java/Kotlin payments platform components, working across these stacks to deliver and maintain secure transaction services.The role operates with advanced technical expertise and high autonomy, developing complex backend features, maintaining service integrity and ensuring the protection of sensitive transactional data within a regulated and compliance‑driven environment.Key ResponsibilitiesBackend Development & Secure Domain OwnershipDesign, develop, and maintain payment-oriented backend services across both PHP (e‑commerce gateway) and Java/Kotlin (core payments platform) codebases Contribute to core payment backend applications with a strong focus on security-sensitive transaction flows. Identify gaps or limitations in core backend services and propose technical solutions aligned with business needs. Analyze business and technical requirements to assess feasibility and implementation impact. Own backend components end-to-end, from design and implementation through production support. Act as a co‑owner of the PHP e‑commerce gateway, sharing accountability for its evolution, security and reliability. Security, Reliability & Performance Apply secure coding practices appropriate for transaction-critical and sensitive data environments. Support the implementation of payment protocols and security-related service interactions. Participate in incident analysis and troubleshooting related to payment services. Ensure backend services meet reliability, performance, and data integrity requirements. Critically review AI-assisted code for security, correctness and compliance before it reaches production, treating AI output as a draft to be validated rather than trusted by default. Ensure no sensitive transactional data, secrets or regulated information is exposed to AI tooling. Testing, Quality & Continuous Integration Design and perform unit and integration testing for payment services. Debug and resolve defects identified during CI pipelines and iterative builds. Maintain and continuously improve test coverage and backend quality standards. Participate actively in code reviews to ensure consistency, quality, and security standards. Use AI coding assistants to accelerate test authoring, refactoring and debugging, while retaining full ownership and accountability for the quality of the delivered code. Collaboration & Delivery Work closely with Product Managers to design and deliver backend solutions using agile methodologies. Collaborate with peer developers, QA engineers, and release teams across the Core Business Domain. Provide technical support for complex production issues and internal problem-solving when required. Continuous Improvement Contribute to improving backend architecture, service interactions, and development practices. Support documentation and knowledge sharing related to Secure Store services. Actively contribute to improving system robustness and long-term maintainability. Help mature the team's practices for effective and responsible AI-assisted development, sharing prompts, patterns and guardrails that improve productivity without compromising security. RequirementsBachelor’s degree in Computer Science, Engineering, or related fields. 7–10 years of total backend development experience, including secure, high‑risk backend systems. 4–6 years in similar senior PHP/Java/Kotlin backend roles, owning production services and developing secure backend features. Experience working with REST-based backend architectures and service-oriented systems. Strong familiarity with development and delivery tools: Git, GitLab, Docker, CI/CD pipelines, and issue-tracking tools. Hands-on experience using AI coding assistants in a professional software development workflow, with an understanding of their security and data-confidentiality implications. Experience working in payments, fintech, or other regulated and security-sensitive environments is a strong plus. Exposure to or ability to collaborate on systems built with Java / Spring Boot is a great plus. Fluent English is mandatory. French and/or Spanish are a plus.