Back-end Developer (Java)

We are seeking a mid-level Back-End Developer to take ownership of complex backend systems, lead technical architecture decisions, and mentor the next generation of developers. You will work with cutting-edge technologies to design, build, and optimize services that impact billions of mobile users worldwide.

This is a hands-on leadership role — ideal for someone who thrives in a fast-moving environment, enjoys collaborating across functions, and is driven to deliver scalable, reliable, and future-proof systems.

This position is based in Warsaw with a hybrid work model. 

Responsibilities:

• Design and develop highly scalable, modular backend applications and APIs using Java and Spring Boot.
• Own the full development lifecycle — from requirements analysis, design, coding, and testing to deployment and monitoring in production.
• Lead initiatives to improve system scalability, performance, and security.
• Collaborate closely with Product, Algo, DevOps, BI, and Marketing to deliver integrated, business-driven solutions.
• Ensure observability through robust logging, metrics, and alerting with tools like Prometheus, Grafana, Kibana.
• Drive adoption of engineering best practices, code quality standards, and technical documentation.
• Mentor and guide junior developers, fostering knowledge sharing and continuous improvement.

Requirements:

• Bachelor’s degree in Computer Science or equivalent practical experience.
• 3 years of professional Java development experience - Must
• Proven track record in designing and delivering complex distributed systems and microservices (Docker, Kubernetes).
• Strong understanding of scalability, concurrency, and performance optimization challenges.
• Hands-on experience with CI/CD tools and automated build/deployment pipelines.
• Proficiency in Spring & Spring Boot frameworks.
• Excellent communication skills and the ability to influence technical direction across teams.
• Experience running applications on Kubernetes, with a focus on designing services that scale efficiently and consume resources effectively (rather than cluster administration).
• Ability to measure and improve application performance using profiling, benchmarking, and APM tools (e.g., JFR, JMeter, Micrometer, New Relic, Datadog).

Will be a plus:

• Background with NoSQL databases (MongoDB, Couchbase) and SQL databases.
• Knowledge of reactive programming (Spring WebFlux).
• Familiarity with monitoring and alerting tools such as Prometheus, Grafana, and Kibana.

What we offer:

• Polish public holidays.
• 20 working days per year is Non-Operational Allowance and settled to be used for personal recreation matters and are compensated in full. These days have to be used within the year, with no rollover to the next calendar year.
• Health Insurance.
• Gym Subscription (Multisport).