Senior Kotlin/Java Developer (Fintech)

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!