About Piano

Piano’s Digital Revenue Optimization solution helps digital services grow revenue by better understanding and influencing their customers’ behavior. Piano unifies analytics, segmentation, and commercial personalization in one AI-driven application, enabling sites and apps to efficiently maximize the value of every user visit. Headquartered in Amsterdam with offices in the Americas, Europe, and Asia-Pacific, Piano serves a global client base including the BBC, Deutsche Telekom, Nikkei, AXA and the Wall Street Journal. For more information, visit piano.io.

About the project

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.

• Critical domain: billing cycles, and subscription lifecycles across multiple payment providers. Precision and data integrity are non-negotiable.
• Distributed architecture: event-driven patterns (Kafka), Outbox patterns, and distributed coordination (Redis/Redisson distributed locks).
• Hybrid ecosystem: mix of Spring Boot + Jersey + Guice, split between Java 21 and Kotlin 2.0.
• Scale & resilience: resilience patterns (Resilience4j), observability (Datadog/OpenTelemetry), and scheduling (Quartz).

What you’ll do

• 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.

Expected qualifications

• 5+ years of experience as a Java Developer (enterprise systems preferred).
• Strong proficiency in Java (up to v21) and plus would be a solid experience with Kotlin.
• Experience with Spring Boot (2.7+) / Spring Framework.
• Good level of 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)
  • 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)

Nice to have

• Cloud/infra: Basic understanding of AWS, Docker/Docker Compose.
• Observability: Datadog, OpenTelemetry, distributed tracing/metrics-first mindset.
• Payments: experience integrating Stripe
• Computer Science degree
• Selenium experience

Current Tech stack

• Languages: Java 21, Kotlin 2.0
• Frameworks: Spring Boot, Guice, Jersey (JAX-RS)
• Data: MySQL 8.0, Redis (Redisson), Hibernate 5.6, DynamoDB
• Messaging: Apache Kafka
• Resilience / Scheduling: Resilience4j
• Observability: Datadog, OpenTelemetry
• Build: Gradle (Kotlin DSL)
• Infrastructure: Docker, AWS, Kubernetes

Employment & benefits

• B2B contract
• Up to PLN 27,000
• Hybrid work model: 2 days/week from the office in Warsaw
• Benefits: 20 days of paid leave, Lunch Card, Luxmed

Recruitment process

1. Screening call (up to 30 minutes, video)
2. Technical Interview
3. Manager Interview