Golang Developer (f/m/x)

We are looking for a Senior Golang Developer to join Sii and work on a large-scale backend system delivered in cooperation with a global organization operating in the US telecommunications market. The project focuses on building and evolving a critical platform that manages registration, verification, and the lifecycle of toll-free numbers used in SMS/MMS campaigns by business customers.

You will contribute to a mature, event-driven system with strong domain logic, multiple external integrations, and real business impact. At Sii, we value long-term cooperation, stability, and continuous growth, offering access to mentoring, knowledge sharing, and further development opportunities across multiple projects.

• At least 5 years of professional experience as a backend or software developer, including Golang
• Strong knowledge of building HTTP APIs and backend services in distributed systems
• Experience with relational databases, particularly PostgreSQL, and data migrations
• Familiarity with event-driven architectures and asynchronous processing (e.g., Kafka)
• English proficiency at B2 level or higher, enabling effective communication in an international environment
• Residing in Poland required

• Design, develop, and maintain backend services and REST APIs supporting customer-facing and administrative systems
• Implement and evolve domain and service layers handling registration workflows, reviews, and lifecycle management
• Integrate with external systems using synchronous APIs and asynchronous event processing
• Work with PostgreSQL databases, including schema migrations and performance-oriented queries
• Contribute to system reliability, scalability, and code quality in a distributed, event-driven architecture

Residing in Poland required