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

SMARTCORE AG; Madrid; A distancia; EUR 70.000 - 90.000; Jornada completa

Descripción de la vacante

A leading fintech company in Madrid is seeking an experienced backend developer specialized in Kotlin and Java. The role involves designing microservices, optimizing high-load systems, and integrating payment solutions. The ideal candidate has over 10 years of experience, expert-level Kotlin skills, and is fluent in Russian. Competitive salary and modern tech stack offered.

Servicios

Competitive salary

Budget for training and professional conferences

Corporate access to top-tier LLMs

Formación

• At least 10 years of commercial backend development experience with Java/Kotlin.
• Expert-level proficiency in Kotlin.
• Deep knowledge of Java Core and the JVM ecosystem.
• Excellent command of Spring Boot.
• Experience with PostgreSQL and MongoDB.
• Hands-on experience building systems with Kafka.
• Experience designing and building distributed, fault-tolerant systems.
• Fluency in Russian for team communication.

Responsabilidades

• Design and develop new microservices and business logic using Kotlin and Java.
• Optimize performance of existing system components.
• Integrate with third-party payment systems and banks.
• Conduct code reviews and mentor junior developers.
• Participate in R&D for new technologies.

Conocimientos

Backend development experience with Java/Kotlin

Kotlin proficiency

Spring Boot

PostgreSQL

Kafka

Microservices architecture

Docker

Fluent in Russian

Herramientas

Kafka

RabbitMQ

Redis

Kubernetes

Descripción del empleo

About the Company : 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.

Feel free to apply directly via LinkedIn or by sending your CV to stanislav.pavlov(@)smartcore.pro — if you’re ready for serious architectural challenges and want to build a product you can be proud of!