Node.js Backend Engineer (Contract)

At Blazity, we are a team of React.js and Next.js experts focused on creating API-first products. We build long-term partnerships with our clients, acting as trusted development partners. Our work includes optimizing apps, stores, and websites, implementing new features, and automating workflows to deliver outstanding results.

For this engagement, we are looking for an experienced Node.js + TypeScript Engineer for a time-limited project (2–3 months) focused on building a production-grade connector service between two SaaS APIs.

You will work with our internal Node.js + TypeScript + Fastify service template that includes:

• Fastify app scaffolding

• Type-safe configuration

• Dependency injection with Awilix

• OpenTelemetry tracing & metrics

• Swagger / OpenAPI documentation

• Docker & Docker Compose

• Vitest testing environment

Our requirements

• 5+ years of experience building production services with Node.js + TypeScript; familiarity with Fastify or similar frameworks.

• SaaS integrations: designing connectors/plugins between APIs (auth, data mapping, pagination, rate limits, idempotency, webhooks).

• Quality & Ops: GitHub flow/PR reviews, CI; automated tests with Vitest (unit/integration/e2e using Fastify inject).

• Observability: practical experience with OpenTelemetry traces/metrics and structured JSON logging.

• Data & privacy: careful handling of PII (redaction/masking in logs, scoped access).

• Documentation: clear runbooks and lightweight user guides.

Nice to have 

• Familiarity with the two target APIs’ objects/events and i18n/translation pipelines.

• Experience deploying containerized services to a managed platform.

Scope of responsibilities

• Implement auth flows (OAuth2/API key), token storage/refresh, least-privilege scopes.

• Build type-safe mappers between API models; validate requests/responses with schema guards.

• Ensure idempotency and safe retries for outbound calls (exponential backoff + jitter; respect Retry-After; handle 429/5xx).

• Add observability: request/correlation IDs, traces, and key business metrics (events processed, retries, dedupes).

• Ship tests (unit/integration/e2e using Vitest and Fastify’s inject) and harden error handling.

• Produce handover: runbook, env/setup steps, API mapping spec, and error taxonomy.

What we offer

What Makes Us Special?

📈 Our team has a genuine impact on the company’s decisions and direction.

✨ No bureaucracy – we keep things simple and efficient.

🗺️ Remote work from Poland

Salary ranges

B2B: 120-160 PLN net+VAT / h 

Location

🗺️ Remote work from Poland