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Salary
≈ $34k – $85k per year (Estimated)
Location
In office (Lisbon)
Seniority
Senior · 3+ years exp
Employment
Full-Time

Confirmed on the employer's own hiring board on Oct 23, 2026. First seen by Alion on Aug 28, 2026.

Overview
Company
Impact
Profile match

99X

99X provides product engineering and digital innovation services. Its teams build software for Nordic and European technology companies. The company is known for a strong engineering culture.

We are looking for a Backend Java Engineer to join our team and help design, develop, and maintain scalable, high-performance backend services that support critical business applications.

In this role, you will be responsible for building robust and efficient solutions, ensuring code quality, and contributing to the continuous improvement of our software development practices. You will work closely with cross-functional teams in a dynamic and international environment.

The role combines backend development, software engineering best practices, and operational excellence, with a strong focus on scalability, maintainability, and performance.

Responsibilities:

Design, develop, and maintain scalable backend services and APIs using Java frameworks such as:

  • Quarkus
  • Spring Boot

Ensure application reliability, performance, and scalability across all environments

Promote and implement continuous improvement initiatives within the software development lifecycle

Apply software engineering best practices to:

  • Develop high-quality code
  • Improve maintainability
  • Increase development efficiency

Analyze, troubleshoot, and resolve complex application issues

  • Conduct root cause analysis
  • Perform post-mortem activities to prevent recurrence

Monitor and optimize application performance and resource utilization

Support the evolution of backend architecture and future technical decisions

Ensure code quality through:

  • Automated testing
  • Peer code reviews
  • Clean Code principles

Collaborate with:

  • Developers
  • Architects
  • Product Owners
  • Managers
  • External stakeholders

Ensure timely delivery and alignment across distributed teams

Participate in production support and incident resolution activities when required

Requirements:

3+ years of experience in a Backend Software Engineering role

Strong knowledge of Java fundamentals, including:

  • Collections
  • Classes
  • Interfaces
  • Enums
  • Inheritance
  • Exception handling

Hands-on experience in the design, development, and operation of scalable backend services using:

  • Quarkus
  • Spring Boot

Solid understanding of:

  • Databases
  • Transaction management
  • Data persistence concepts

Experience ensuring code quality through:

  • Automated testing
  • Code reviews
  • Clean Code principles

Strong experience in:

  • Performance optimization
  • Troubleshooting production environments
  • Root cause analysis

Excellent problem-solving and analytical skills

Ability to work with:

  • Autonomy and ownership
  • Proactivity and leadership
  • Collaboration and a continuous improvement mindset

Excellent communication and interpersonal skills

Strong presentation abilities

Team-oriented attitude

Fluent English proficiency (mandatory, minimum B2 level)

Nice-to-have:

Degree in Computer Engineering, Computer Science, or a related field

Experience with cloud environments (preferably Azure)

Knowledge of containerized applications and microservices architectures

Experience with CI/CD pipelines and DevOps practices

Familiarity with Agile methodologies

Experience working in large-scale or enterprise environments

Strong focus on innovation, automation, and continuous improvement

If this sounds like you, share your CV with us and let's talk!

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