Backend Engineer - API Development (TypeScript / Node.js)

As a preferred supplier to one of our biggest Financial Client, I am seeking for a Backend Engineer - API Development (TypeScript / Node.js) for a position in Amsterdam, Netherlands. The successfully candidate is an independent backend engineer to help build, harden, and scale our secure APIs - strong on API craft, security, and testing, and able to help drive delivery, not just execute tickets.

Where you add the most value:

Since internal logic is covered, their leverage is on the partner-facing platform and developer experience:

• Growing the API surface cleanly (new endpoints, webhooks/callbacks, richer querying)
• Scaling - repeatable multi-partner onboarding, tenant isolation, load/performance testing, caching
• Platform quality - SLOs, alerting, resilience patterns

Ways of working:

• Independent and self-directing - takes a capability from spec -> design -> tested delivery without hand-holding
• Helps manage the work - can break down a body of work, sequence it, and drive it to a clear \"done\"
• Spec- and documentation-driven - at home working from and writing specs, acceptance criteria, and decision records; a clear, concise writer
• Comfortable with AI-assisted / agentic development - this project is built heavily with agentic tooling; someone who can direct and review that output well is a real multiplier
• Quality-first and pragmatic - treats security, testing, and observability as ship-blocking, while favoring simple solutions over over-engineering

Core skills requirement:

• REST/JSON API design - versioning, consistent error contracts, idempotency, pagination, and an API-as-contract mindset (OpenAPI)
• Relational data - schema design, migrations, and a data-integrity mindset
• Asynchronous & queue-driven systems - background workers, job lifecycles, retries, idempotent processing
• API security - token-based auth (OAuth/JWT), authorization and tenancy isolation, secure secret handling, \"fail-closed\" defaults, and awareness of industry baselines (e.g. OWASP API Security Top 10)
• Test-forward development - comfortable driving work through unit, integration, and contract tests as a first-class part of building, not an afterthought
• Hands-on AWS experience (mandatory) - must know the specifics of core AWS services (containers/compute, queuing, managed databases, secrets, load balancing). Given the short timeline and MVP nature, we prefer they not need to onboard onto a new cloud;
• Cloud-native delivery - building and shipping containerized services, infrastructure-as-code (Terraform ideal), CI/CD pipelines
• Observability - structured logging, metrics, tracing, and audit trails; can debug production from telemetry

Nice-to-haves:

• fintech or other regulated-domain experience