Senior Node.js developer

About the Position

We are seeking a Senior Node.js Developer with over 6 years of experience to join our client, a full-service telecommunications provider, in Plovdiv or Sofia, Bulgaria. In a Hybrid role, you will build and own the server-side microservices of our client's new BSS platform.

Responsibilities

• Design and build the Eligibility and Cost-Optimization Engine - queries QMC Available Services API, applies cost-priority matrix logic, returns cheapest available product at a given address.
• Build the Swiss QR-invoice microservice: consumes Lago invoice.created webhooks, generates QR-invoice PDFs per SIX Group specification using Gotenberg.
• Implement the event-driven notification service (email and SMS) across order, billing, and payment lifecycle events.
• Own the integration with the QMC Provisioning API - triggering technical product activation from order events with error handling and observability.
• Define REST API contracts with the Frontend Engineer from Sprint 0. Maintain API documentation throughout.
• Instrument all services with OpenTelemetry for end-to-end distributed tracing to DataDog.
• Enforce 90% unit test coverage on all new code.

Requirements

• Node.js / TypeScript: 6+ years building production microservices. Strong async patterns, event-driven architecture.
• REST API and webhook design: Experienced designing and documenting contracts consumed by frontend and third-party systems.
• Event-driven integration: Message bus experience (Kafka, RabbitMQ, or NATS). Webhook producer/consumer patterns.
• PostgreSQL: Production experience. Query optimization, schema design, migrations.
• Docker / Kubernetes: Confident containerizing services and writing Kubernetes manifests or Helm values.
• OpenTelemetry: Hands-on instrumentation of Node.js services for distributed tracing.
• Testing: Jest or equivalent. Integration testing across service boundaries, contract testing awareness.

Nice to Have

• Medusa.js v2 backend module experience or any headless commerce platform.
• .NET / C# reading ability for QMC integration collaboration.
• Lago or subscription billing API experience.
• PDF generation experience (Gotenberg, Puppeteer).
• German or French language skills.

We Offer

• Remote work with occasional office visits
• An open, transparent, and fun work culture.
• Multi-national team and collaborative work environment.
• Continuous knowledge sharing with engaged co-workers.