Senior Java Engineer

Ready to embark on the quest of joining Hack The Box?

At the end of this journey, you'll become a proud member of Hack The Box, with the ultimate mission to raise cyber resilience, so that every organization can stay ahead of tomorrow’s threats.🚀🔒💻

✨The core mission of the Senior Java Engineer:

Your mission is to design and implement the microservices foundation that will transform how we build and ship software. You'll bring the judgment to apply the right patterns at the right time, whether that's designing domain-driven aggregates, implementing sagas for distributed consistency, or establishing a unified API Gateway layer to manage routing, security, API composition, and cross-cutting concerns. You'll lead by example: creating robust, secure Spring Boot services and helping teams adopt resilience and integration patterns (circuit breakers, transactional outbox, messaging) as second nature.

In the next months, you'll shape foundational architectural decisions, decomposition strategies, service boundaries, messaging infrastructure, and the patterns that ensure data consistency across domains. You'll apply refactoring patterns like strangler and anti-corruption layer to safely evolve legacy systems without disruption. Within the year, your contributions will directly translate into a platform where quality, security, and speed reinforce each other, creating lasting impact for users and the business.

🏢 Location & Work Mode:

• Europe/Greece

• Choose between fully remote work across Europe or relocating to our Athens Tech Hub with relocation support.

Fully Remote / Hybrid (2 days in the office, 3 days remote, plus one month of work from anywhere) - If only in Greece: When hiring in Greece, we’re open to candidates from all locations. Those based within 55 km of our Athens office will follow a hybrid work model. For candidates located beyond that radius, a fully remote arrangement is available.

✈️ Relocation

• We offer a 10% relocation bonus on the annual salary to support your move.
• In addition, you would benefit from a 50% tax reduction on your income as part of the relocation.
• We'll support you with accommodation during the first few weeks

🍺 The fellowship you’ll be joining:

You'll join a fully autonomous, high-performing team of senior engineers and architects, backend-oriented but T-shaped, meaning you'll find people who can stretch across boundaries when needed. The team operates with an agile mindset, taking ownership end-to-end and holding themselves to high standards of quality and craftsmanship. This is a group that moves fast, takes pride in what they build, and continuously raises the bar.

Collaboration is central to this role. You'll work closely with SRE/Infrastructure to ensure reliability and operational excellence, Platform teams to align on shared foundations, and QA to maintain high quality standards. You'll also partner with Data, Analytics, and AI teams to enable data-driven capabilities and ensure seamless integration across the platform. On the business side, you'll engage with Product teams, Product Owners, and Business stakeholders to ensure technical decisions are grounded in real user and business needs.

You'll report to Senior Architects, giving you direct access to strategic technical leadership and the opportunity to influence architectural direction at scale.

⚔️ Technology tools & weapons you’ll be using:

Java, Kotlin, Spring ecosystem, API integration styles, Relational databases, noSQL, Docker, Kubernetes, Git, GitHub, Jira

📚 Interesting resources you should check:

• Tassos's journey into engineering
• R&D team meetup

🚀 The adventures that await you after becoming Senior Java Engineer at Hack The Box:

• Design and build new Spring Boot microservices, applying patterns that ensure consistency, resilience, and scalability.
• Shape the API Gateway layer, enabling secure routing, composition, and cross-cutting concerns for our platform.
• Collaborate with architects and teams to define service boundaries and integration strategies aligned with business needs.
• Modernize legacy systems incrementally using strangler fig and anti-corruption layer patterns, no big bang rewrites.
• Champion code quality through reviews, best practices, and hands-on guidance that elevates the entire team.
• Partner with SRE, Platform, and QA to keep services observable, testable, and production-ready.
• Contribute to architectural decisions, documenting trade-offs and communicating direction clearly.
• Mentor fellow engineers, sharing knowledge on microservices, Spring ecosystem, and clean code practices.

🏆 Skills, knowledge, and experience points required to unlock the role of Senior Java Engineer at Hack The Box:

• Solid experience with Java and the Spring ecosystem (Spring Boot, Spring Cloud, Spring Data, Spring Security) in production environments.
• Hands-on experience designing and building microservices, with practical knowledge of patterns like Saga, CQRS, Transactional Outbox, and API Gateway.
• Strong understanding of distributed systems challenges—data consistency, service communication, resilience, and fault tolerance.
• Experience with messaging systems (e.g., Kafka) and event-driven architectures.
• Familiarity with containerization and orchestration (Docker, Kubernetes) and CI/CD pipelines.
• Ability to communicate architectural decisions clearly, whether through diagrams, documentation, or conversations with technical and non-technical stakeholders.
• A track record of mentoring or guiding other engineers—you don't just write great code, you help others do the same.

🕹️ What your Hack The Box adventure will have in store:

• 🎯You'll have the exhilarating opportunity to contribute to a product that is highly appreciated by users and the cybersecurity community at large.
• 🎯 You'll experience a highly supportive and caring environment, fostering growth, flexibility, and autonomy.
• 🎯 You'll embark on an exciting journey of continuous learning and problem-solving, levelling up as our organisation grows.
• 🎯 Most importantly, you'll have a blast at HTB 🥳 because fun is an essential ingredient in our recipe for success! Just wait until you see our global meet-ups!

💰 The gems you’ll be enjoying as Senior Java Engineer:

• Private insurance
• 25 annual leave days
• Dedicated budget for training and professional development, participation in conferences
• State-of-the-art equipment (Macbook, iPhone, and mobile plan)
• Free lunch & snacks at the office
• Full access to the Hack The Box lab offerings; so you can learn how to hack
• Flexible/Hybrid working

Note after Benefits:

Our benefits package is designed to provide strong support to our team, but it may vary depending on location and type of employment (e.g., UK, US, Greece, Australia, or engagement through an Employer of Record or contract).

🗺️ The Quest of Becoming Hack The Box’s Senior Java Engineer:

• Level 1: To complete level one’s objective, submit your application.
• Level 2: Meet the Talent Acquisition team. Level’s objective: highlight your past achievements, ambitions, and values.
• Level 3: Meet the hiring team. Level’s objective: connect with the hiring team and share with them your achievements.
• Level 4: Complete an assignment that aligns with day-to-day job-related tasks and responsibilities. Part of the assignment is discussing it with the hiring team in a debriefing session, in order to walk the team through your thinking process.
• Level 5: You've officially received an offer from HTB! To complete the last level and the Quest, all you need to do is accept the offer.

Hack Your Career, Today. Join us in this epic adventure of cybersecurity at Hack The Box! 🚀🔒💻

At Hack The Box, we are on a quest to find the most exceptional and enthusiastic talent to join our team. Whether or not you consider yourself a gamer, we value what makes you unique and want to know more about you. This job post provides just a glimpse of the incredible gamified experience our business and consumer customers enjoy through our platforms. So, if you're ready to embark on a journey of growth and adventure, we can't wait to meet you!

ABOUT HTB:

Hack The Box (HTB) is the cybersecurity upskilling and talent development platform trusted by individuals, enterprises, and government agencies to sharpen offensive and defensive capabilities. Powered by a vibrant global community and hands‑on, real‑world training, HTB helps security teams practice like attackers, validate skills continuously, and move faster against emerging threats. We’re scaling rapidly across the enterprise market—especially in Financial Services, MSSPs, and Technology—and we’re just getting started.

If you’re excited to turn technical depth into crisp stories, to shape a category, and to fuel measurable growth in a fast, collaborative environment—come build with us.

🚨 Exciting News:

• Get the most important updates on HTB’s latest year!
• We are super proud to share that Hack The Box’s entities in the US, the UK & Greece have been certified as a Great Place to Work (2024-2026).
• Furthermore, Hack The Box’s Greek entity has been listed by the Great Place to Work Institute in the Top 5 of Best Workplaces for three consecutive years (4nd, 2nd, 3rd)
• On the European level, the Greek entity has been listed as Best Workplace in Europe for three consecutive years
• Take a sneak peek at how it is to be part of HTB and our 2023 Global Retreat. Get more insights about our HTB culture and employee experience by visiting the “about us” section of our site, our career site, and Glassdoor.

At Hack The Box, we are committed to fostering a diverse, inclusive, and equitable workplace. We believe that diversity enriches our performance, services, and the communities we serve. As such, we ensure that all job applications are considered solely based on merit, skills, and qualifications. We do not discriminate on grounds of race, color, religion, gender, gender identity or expression, sexual orientation, national origin, genetics, disability, age, or veteran status. We are dedicated to providing a fair and respectful work environment that reflects our values.