Senior Kotlin/Java (Fintech) – remote friendly (EMEA)

SMARTCORE AG; Barcelona; Presencial; EUR 90.000 - 150.000; Jornada completa

Ventajas ofrecidas por este puesto de trabajo

Competitive salary

Modern tech stack

Training budget & conferences

Access to top-tier LLMs

Descripción de la vacante

SmartCore AG is building a scalable core acquiring platform for a fast-growing fintech. You will design and implement microservices in Kotlin/Java, focusing on high performance, fault tolerance, and security. You will work with Kafka/RabbitMQ, PostgreSQL, MongoDB, and modern containers in a distributed team.

The role requires deep JVM, Spring Boot expertise, and strong problem-solving skills. You will mentor peers, participate in R&D and ensure high-quality code with tests, while collaborating

Formación

• 10+ years of backend development experience with Java/Kotlin.
• Expert in Kotlin idioms, coroutines, functional features and practical use.
• Deep knowledge of Java Core and the JVM ecosystem.
• Excellent command of Spring Boot including REST APIs, auto-configuration, Spring Security and Actuator.
• Expert in PostgreSQL: complex schemas, query optimization, isolation levels and replication.
• Experience with MongoDB.
• Hands-on experience with Kafka (brokers, producers/consumers, delivery guarantees).
• Familiar with RabbitMQ and Redis (caching, pub/sub, distributed locks).
• Experience building distributed, fault-tolerant microservices (CQRS, Event Sourcing).
• Comfortable with AI technologies and applying LLMs in practice.
• Knowledge of networking protocols (TCP/IP, HTTP/2, gRPC).
• Experience with Docker/Kubernetes for containerization/orchestration.
• Writes clean, maintainable, well-tested code.
• Highly autonomous and accountable for product quality.
• Fluent in Russian (B2+).

Responsabilidades

• Design and develop new microservices and business logic using Kotlin and Java.
• Optimize performance of high-load system components and code areas.
• Make architectural decisions to improve fault tolerance, scalability and security.
• Integrate with third-party payment systems, banks, and processing centers.
• Work with asynchronous data streams using Kafka and RabbitMQ.
• Conduct code reviews, mentor colleagues and promote best practices.
• Participate in R&D to evaluate new technologies for the stack.
• Write unit and integration tests to maintain a high-quality codebase.

Conocimientos

Java/Kotlin backend

Kotlin coroutines

Spring Boot

PostgreSQL

MongoDB

Kafka

RabbitMQ

Redis

Microservices architecture

CQRS & Event Sourcing

Docker & Kubernetes

Distributed systems

Russian language

Code quality & tests

AI/LLM integration

Herramientas

Docker

Kubernetes

Kafka

RabbitMQ

Redis

PostgreSQL

MongoDB

Spring Boot

gRPC

Descripción del empleo

SmartCore is a fintech holding building infrastructure for the next generation of payments. Our solutions cover the entire financial operations cycle - from core banking and processing to cards, wallets, and anti-fraud systems.

We are a leading fintech company developing innovative solutions in payment processing and anti-fraud technologies. We create high-tech products that are reshaping the financial landscape and are looking for true professionals ready to tackle complex and ambitious challenges.

About the Project:

You'll join a key team responsible for developing and evolving our core acquiring platform - a complex, high-load, microservices-based system operating 24/7. We handle the entire payment lifecycle, from initiation to clearing, ensuring minimal latency, high fault tolerance, and full compliance with strict security standards (PCI DSS).

What You'll Do:

• Design and develop new microservices and business logic using Kotlin and Java.
• Optimize the performance of existing system components and handle high-load areas of the codebase.
• Make key architectural decisions aimed at improving fault tolerance, scalability, and platform security.
• Integrate with third-party payment systems, banks, and processing centers.
• Work with asynchronous data streams using Kafka and RabbitMQ.
• Conduct code reviews, mentor less experienced colleagues, and promote best development practices.
• Actively participate in R&D - exploring and integrating new technologies into the project stack.
• Write unit and integration tests to maintain a high-quality codebase.

Our Ideal Candidate:

• Has at least 10 years of commercial backend development experience with Java/Kotlin.
• Demonstrates expert-level proficiency in Kotlin: understands idioms, coroutines, functional features, and applies them effectively.
• Possesses deep knowledge of Java Core and the JVM ecosystem.
• Has excellent command of Spring Boot - not only building REST APIs but also understanding its internals, auto-configuration, Spring Security, and Actuator.
• Expert in PostgreSQL - experienced in designing complex data schemas, optimizing queries, understanding transaction isolation levels, and replication mechanisms.
• Experience with MongoDB.
• Hands-on experience building systems with Kafka - understanding broker mechanics, producer/consumer patterns, and message delivery guarantees.
• Familiar with RabbitMQ and Redis (including caching, pub/sub, and distributed locks).
• Experience designing and building distributed, fault-tolerant systems (microservices architecture, CQRS, Event Sourcing).
• Comfortable with modern AI technologies, including AI agents, and capable of applying various LLMs in practice.
• Understanding of networking protocols (TCP/IP, HTTP/2, gRPC).
• Experience with containerization and orchestration tools (Docker, Kubernetes).
• Writes clean, maintainable, and well-tested code.
• Highly autonomous, proactive, and takes full ownership of product quality and outcomes.
• Fluent in Russian (B2 or higher) - required for daily communication within the team.

Nice to Have:

• Experience in fintech or payment processing; familiarity with PCI DSS.
• Experience with reactive stacks (Project Reactor, WebFlux).
• Familiarity with monitoring and tracing tools (Prometheus, Grafana, Jaeger).
• Experience with load testing tools (JMeter, Gatling).

We Offer:

• A competitive salary, discussed individually with each candidate.
• A modern technology stack and minimal bureaucracy.
• Budget for training, professional conferences, and books.
• Corporate access to all top-tier LLMs with maximum configurations.
• A team of passionate experts where your voice will always be heard.