Senior Back End Engineer (Java, Kotlin, Python, Node.js, Golang, or C#) (Fintech/PSP) – remote friendly (EMEA)

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.
• 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 5 years of commercial backend development experience using one of the following languages: Java, Kotlin, Python, Node.js, Golang, or C#.
• Has practical experience with any SQL database (PostgreSQL, Oracle, MySQL, etc.), including optimizing queries and understanding transaction isolation levels.
• Hands-on experience building systems with Kafka — understanding broker mechanics, producer/consumer patterns, and message delivery guarantees.
• Experience in system design and architecture of distributed, fault-tolerant systems.
• 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.
• Comfortable with modern AI technologies, including AI agents, and capable of applying various LLMs in practice.
• Experience with NoSQL databases (MongoDB, Redis).
• Familiarity with RabbitMQ.
• 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!