Senior Java Developer

Quick Facts

• Domain: billing cycles and subscription lifecycles across multiple payment providers
• Architecture: hybrid monolith + selected microservices; event-driven patterns

Description

You’ll join a team working on a high-complexity system in the billing & subscription management domain. The platform uses a hybrid architecture (monolith + selected microservices) and a hybrid technology stack, requiring strong engineering judgment around consistency, correctness, reliability, and scalability. Precision and data integrity are non-negotiable.

Responsibilities

• Collaborate with technical leaders and architects to efficiently deliver new functionalities in a complex domain.
• Plan, design, and implement new features with a strong focus on reliability, consistency, and maintainability.
• Solve production problems before they affect customer experience (root-cause analysis, mitigation, and long-term fixes).
• Contribute to engineering: testing strategy, performance, observability, and operational readiness.

Requirements

• 5+ years of experience as a Java Developer (enterprise systems preferred)
• Strong proficiency in Java (up to v21); solid Kotlin experience is a plus
• Experience with Spring Boot (2.7+) / Spring Framework
• Good understanding of SQL (MySQL 8) and ORM (Hibernate), including transaction isolation and locking strategies; performance tuning
• Hands-on distributed systems experience: Kafka (event design, consumer reliability, exactly/at-least-once thinking)
• Hands-on distributed systems experience: Redis / Redisson (distributed locks, concurrency handling); designing for eventual consistency, idempotency, and failure scenarios
• Strong automated testing culture: JUnit 5, Mockito, Testcontainers
• Polish, English (B2)

Benefits

• Work in a billing/subscription system where reliability and data integrity are emphasized
• Opportunity to apply resilience patterns (Resilience4j) and observability (Datadog/OpenTelemetry)
• Engineering ownership across testing strategy, performance, observability, and operational readiness

Current Tech Stack

• Java 21, Kotlin 2.0
• Spring Boot, Guice, Jersey (JAX-RS)
• MySQL 8.0, Redis (Redisson), Hibernate 5.6, DynamoDB
• Apache Kafka
• Resilience4j, Quartz
• Datadog, OpenTelemetry
• Gradle (KotlinDSL)
• Docker, AWS, Kubernetes