Senior Backend Engineer (Java)

About Welltech

About Welltech
Welltech is a global wellness technology company with Ukrainian roots. Our mission is to build and scale wellness apps globally through state-of-the-art, tech-driven performance marketing.
We are one of the most established players in the wellness app space, and we are accelerating. Over 25.5 million people across the world use our apps — Muscle Booster, Yoga-Go, and WalkFit — to build healthier habits, move more, and feel better every day. Every subscription represents a real person making a real change in their life, and we take that seriously.
With 500+ people across hubs in Cyprus, Ukraine, Poland, Spain, and the UK, we combine the scale of a market leader and the drive of a team that's just getting started.

Why join us?
Welltech is where your work reaches millions of real people.
We're looking for Well-Makers. You'll own decisions, outcomes, and the learning that comes with both. You'll move fast, because action beats perfection here. You'll say what you think, hear the truth back, and get better for it. And when the targets are big — and they are — you won't chase them alone.
If you want a job, there are easier places. If you want to go big — and do it together — this is it.

Position

We are looking for a Senior Back-end Developer (Java) who is dreaming of developing ambitious tech products. You’ll join our Payments team, a core part of our tech organization that’s building a modern, internal payments platform from the ground up. Our mission is to streamline and future-proof payment operations across the entire business. We're not just maintaining systems—we’re rethinking how payments should work in fast-scaling products.

The team is a highly collaborative, cross-functional group with deep expertise in infrastructure, databases, distributed systems, and back-end engineering. We value autonomy, ownership, and knowledge-sharing, and we’re always looking for new ideas to make our systems smarter, faster, and more secure. You’ll have the opportunity to work on technically rich projects that have real, measurable business impact—and have a lot of fun along the way.

Key responsibilities:

• Collaborate across disciplines: Work closely with cross-functional teams including Frontend/Backend Engineers, Infrastructure, QA (SDET), and Product Managers to design, develop, and deliver innovative solutions that drive real impact.

• Design and implement robust systems: Translate both functional and non-functional requirements into scalable, reliable, and maintainable software. Your code will directly shape user experiences and system integrity.

• Build and operate microservices: Develop, deploy, and maintain high-performance microservices using Spring Boot. Own your services end-to-end—from design and implementation to deployment and ongoing support.

• Operate in cloud-native environments: Manage deployments and configurations across various Kubernetes clusters, ensuring smooth rollouts and minimal downtime in production and staging environments.

• Champion system excellence: Take responsibility for the performance, scalability, security, and data consistency of the systems your team owns. Proactively identify bottlenecks and propose architectural improvements.

• Drive engineering best practices: Promote clean code, test automation, continuous integration, and DevOps principles. Help elevate the engineering culture through thoughtful code reviews, tech talks, and collaboration.

• Mentor & lead by example: Provide guidance to team members, lead team level product and engineering initiatives, influence coding standards, support your team in making critical decisions

Your qualification

• Proven Java expertise: At least 5 years of hands-on experience building robust, high-performance applications using Java in production environments.

• Microservices architecture knowledge: A strong grasp of microservices principles, with a track record of designing and scaling distributed systems effectively.

• Spring Boot mastery: Deep, practical experience with the Spring Boot ecosystem—particularly with Spring MVC, RESTful services, Spring Data, Security, and messaging integrations.

• Database skills: Solid experience working with relational databases like PostgreSQL, including an understanding of relational database design, query optimization, and overall data architecture.

• Cloud infrastructure and Cloud-native deployment experience: Previous experience with AWS or another major cloud provider; practical experience deploying and managing services in Kubernetes across multiple environments (e.g., dev, staging, production).

• API and communication protocol fluency: Comfort working with REST, gRPC, messaging systems, and asynchronous communication patterns.

• CI/CD and DevOps mindset: A solid understanding of modern CI/CD pipelines, quality gates, and automation practices that support fast, safe releases.

• Quality-first approach: Demonstrated experience writing comprehensive unit, integration, and API tests for microservices-based systems.

• High proficiency in both written and spoken English, enabling seamless collaboration in an international team.

Will be a plus

• Fintech domain experience: Previous experience working on fintech products or platforms, with an understanding of industry-specific challenges such as security, compliance, payment processing, and subscription billing.

• Stream processing knowledge: Proficiency with Kafka and Kafka Streams for real-time data processing and event-driven architecture.

• Modern app design principles: Familiarity with The Twelve-Factor App methodology and its application in cloud-native service design.

What we offer

• Grow Together: Join a culture that champions both personal and professional growth. Here, you’ll thrive as we learn, evolve, and succeed together.

• Lead by Example: No matter your role, your leadership matters. Every team member is empowered to inspire and make an impact.

• Results-Driven: We’re all about achieving meaningful outcomes. It’s not just about the effort, but the difference we make every day.

• We Are Well-Makers: Be part of a movement that’s creating a healthier, happier world. Together, we make well-being a reality!

Additional details

Candidate journey: Recruiter call --> Live Code Review -->  System Design interview---> Meet the hiring manager

Check out some of our products

Muscle Booster — https://musclebooster.fitness/ 

Yoga-Go — https://yoga-go.io/ 

WalkFit - http://walkfit.pro