Senior Full Stack Java Engineer
First seen by Alion on Oct 11, 2026.
We are looking for a Senior Full Stack Engineer (Java + React) for our partner, a growing software company based in Spain.
Our partner combines product development with client-facing engineering work. They build their own products in the search and AI space while also delivering software solutions for enterprise customers.
As part of an international engineering team, you will work on a live production platform used by real customers, contributing across both backend and frontend development and playing a key role in the evolution of its architecture.
This is a full-time remote contract position with an initial commitment of at least six months and the possibility of long-term extension.
Responsibilities
Design, develop, and maintain backend services and APIs using Java and Spring Boot.
Develop and maintain modern frontend applications using React.
Build and deliver end-to-end features across the backend and frontend.
Participate in a major platform migration toward a more secure and modern architecture.
Contribute to architectural and technical design decisions.
Transform business requirements into scalable technical solutions.
Improve and refactor existing systems while maintaining production stability.
Work with AWS infrastructure and cloud-based production environments.
Collaborate closely with QA and cross-functional teams throughout the development lifecycle.
Participate in Agile ceremonies and planning activities.
Use AI-assisted development tools as an integral part of the engineering workflow.
Requirements
Technical Skills
6+ years of professional software engineering experience.
Strong hands-on experience with Java and Spring Boot.
Strong hands-on experience with React and modern frontend development.
Strong hands-on experience with AWS and building or deploying production applications in AWS environments.
Proven experience building and maintaining production-grade APIs and web applications.
Solid understanding of software architecture, system design, and data modeling.
Good understanding of frontend architecture, component-based development, and API integration.
Experience with Docker, CI/CD pipelines, and modern cloud-native development practices.
Experience working on live products with real production workloads.
AI & Modern Engineering Expectations
Strong hands-on experience using AI-powered development tools such as Claude Code or similar as part of the day-to-day engineering workflow.
Up-to-date understanding of modern AI capabilities and their practical application in software development.
Ability to use AI tools to accelerate development, improve code quality, support architectural decisions, and increase engineering productivity.
Experience with Spec-Driven Development (SDD) or similar methodologies that enable AI-native development workflows.
Ability to identify opportunities where AI can add meaningful value to the product and its users.
Comfortable working in an engineering environment where AI-assisted development is an integral part of the software development lifecycle.
Communication
English level B2 or higher.
Ability to communicate technical concepts clearly to both technical and non-technical stakeholders.
Strong written communication and documentation skills.
Comfortable working within distributed international teams.
Personal Qualities
Strong ownership mentality and proactive approach.
Ability to identify issues early and drive solutions independently.
Open-minded and adaptable when evaluating technologies and approaches.
Focus on code quality, maintainability, and long-term sustainability.
Collaborative attitude and strong teamwork skills.