Senior Java Engineer

B2B | Hybrid | Location: Gdańsk or Warsaw (1–2 times every two months in the office )

Project: Modernization of a banking system

Rate: 30-50€/h

We’re looking for a Java Engineer/Data Engineer to join a project focused on modernizing and optimizing a long-standing legacy system. The current architecture cannot keep up with growing business demands, and the goal is to reach ~2,500 requests per second through deep analysis, refactoring, and architectural improvements.

You will work in a team of 6 experienced engineers on 4 microservices, playing a key role in performance engineering.

data integration, and modernization of Kafka-based components.

Responsibilities:

• Analyze current performance and implement improvements to achieve target throughput (~2,500 req/s).

• Optimize communication between microservices and work with distributed systems.

• Improve data flows (Kafka) and refactor legacy components.

• Develop APIs and service components.

• Collaborate closely with the team in a client-facing environment.

• Address data quality and consistency issues.

• Prepare the system for increased load with a deadline in April 2026.

  
  

Requirements:

• Minimum 5 years of experience as a Java Engineer / Data Engineer.

• Strong experience with Java 21 and the Spring Framework (ideally v3).

• Solid, hands-on experience with Apache Kafka, especially in distributed systems. Must understand internal Kafka mechanisms and know how to diagnose and resolve performance issues.

• Experience with databases, optimization, and potentially sharding.

• Experience in API development and data engineering (data transmission and processing).

• Strong knowledge of architectural patterns (DDD, event-driven, CQRS, etc.).

• Experience creating load tests with Kafka is a strong plus.

About Scalac: 

For over 10 years, Scalac has been delivering high-quality software, successfully aiding FinTechs, HealthTechs, EdTechs, AdTechs, and startups in their efforts to scale. What’s our secret? There is none - just choosing the best technologies and connecting you with the top specialists to implement them. All done by working remotely! 

With over 50 experts on board, from 13 different countries - in Scala, Java, Spark, Rust, Akka, React, Angular, Kafka, blockchain, and more - there is no project we couldn’t enhance, no process we’re not able to support, and no software we couldn’t deliver from start to finish.

Sounds like a fit?Apply now and join our team!