Senior Backend Developer (Java 21/Springboot)

We serve a diverse array of local and international brands both online and in-store, spanning various sectors. We have developed services that focus on revenue optimisation, performance enhancement, fraud prevention, and seamless payment orchestration. 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.

Backend Development & Secure Domain Ownership

Design, 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. 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. 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. 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. Work closely with Product Managers to design and deliver backend solutions using agile methodologies. Provide technical support for complex production issues and internal problem‑solving when required. Contribute to improving backend architecture, service interactions, and development practices.

Bachelor’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.
• ~ 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.
• ~ 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.

it is a shared responsibility. Competitive salary package with a permanent contract Flexible working hours and a wellbeing‑focused intensive summer schedule. Free language courses (Spanish, French, English) to support your global career Involvement in exciting and innovative fintech projects

We believe in equal employment opportunity, a culture built around gender-balanced development opportunities for our professionals, a flexible and healthy working environment, and general equality in the workplace.

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