Senior Software Engineer (Backend): Crypto Payments

Role overview Build and operate backend services that coordinate crypto and stablecoin payments, conversions, and transfers across assets and blockchain networks. The team owns services end to end and is evolving a business-critical platform toward reliable, scalable services and unified APIs. The work includes production operations and collaboration across product, engineering, compliance, and operations; the source describes a hybrid or remote arrangement.

Responsibilities - Design and run high-throughput services for crypto pay-ins, payouts, conversions, and transfers. - Develop versioned, documented APIs for merchants, partners, and internal services. - Protect payment correctness with patterns such as idempotency, transactional outbox, retries, and dead-letter handling. - Improve performance across service calls, databases, and high-traffic paths while modernizing legacy components safely. - Build asynchronous, event-driven workflows with clear contracts between services. - Own production operations, monitoring, incident response, and root cause analysis; contribute to on-call and mentor peers in design and code reviews.

Requirements - Professional backend engineering experience building and operating production systems at scale. - Strong Java skills, ideally Java 17 or later, and Spring Boot; Kotlin is an advantage. - Hands-on experience with microservices, event-driven systems, and brokers such as Kafka or SQS. - Strong relational database experience, including schema design, indexing, query tuning, and safe migrations. - Experience with AWS, Docker, Kubernetes, CI/CD, and observability for metrics, tracing, and logs. - Background in payments, banking, or other financial systems where reliability, auditability, and correctness matter; strong testing, communication, and ownership skills. - Willingness to participate in an out-of-hours on-call rotation and use AI coding tools in design, implementation, and testing.

Nice to have - Experience with stablecoins, blockchain networks, crypto wallets, or crypto payment processing. - Redis or other caching experience, domain-driven design, modular refactoring, or workflow tools such as Temporal. - Experience with rule engines or scheduling systems.

Benefits and work setup The source describes flexible hours and hybrid work, flexible holiday, travel opportunities, and salary ranges by location: €70,000–€110,000 in Bulgaria, €85,000–€110,000 in Spain, and PLN 250,000–480,000 in Poland. Compensation depends on experience and relevant certifications.