API Developer

Backend Engineer – API Development

For a fast-growing financial services scale-up, we are looking for an experienced Backend Engineer with a strong focus on Node.js, TypeScript, AWS and API development.

You will work on a partner-facing API platform used in a financial environment where security, reliability and testing are critical. The role is suited to someone who can independently take a capability from specification through design, implementation, testing and production delivery.

This is a long-term secondment opportunity through IQ Staffing.

You will help expand, harden and scale a modern API platform. The internal business logic is already covered by the existing team, so your focus will be on backend engineering, API quality, partner integrations and developer experience.

You will have a high degree of ownership and are expected to help structure the work, make technical decisions and drive delivery rather than only execute predefined tickets.

Design and develop new REST API endpoints, webhooks and callbacks

Improve API contracts, versioning, error handling and querying capabilities

Build and maintain clear API specifications and integration documentation

Improve developer experience for external partners and integrations

Implement secure authentication, authorization and tenant isolation

Strengthen API security through rate limiting, secret management and secure defaults

Build reliable asynchronous and queue-driven workflows

Implement retry, idempotency and resilience patterns

Improve unit, integration and contract testing

Support load, performance and scalability testing

Build and maintain CI/CD pipelines and Infrastructure as Code

Improve logging, monitoring, tracing, alerting and auditability

Resolve security and penetration-test findings

Help establish repeatable onboarding for multiple external partners

Strong backend development experience with TypeScript and Node.js

Solid experience building production-grade HTTP services and REST/JSON APIs

Strong understanding of API design, including versioning, pagination, idempotency and consistent error contracts

Experience with API specifications such as OpenAPI

Experience with relational databases, schema design and migrations

Strong understanding of data integrity and transactional consistency

Experience with asynchronous and queue-based systems

Knowledge of background workers, retries and idempotent processing

Strong understanding of API security, including OAuth, JWT, authorization and secure secret handling

Awareness of security standards such as OWASP API Security Top 10

Strong experience with unit, integration and contract testing

Hands-on AWS experience is mandatory

Practical knowledge of AWS services around compute/containers, queues, managed databases, secrets and load balancing

Experience with containerized applications, CI/CD and Infrastructure as Code

Terraform experience is preferred

Experience with structured logging, metrics and distributed tracing

Able to work independently and take ownership from specification to production

Comfortable with AI-assisted or agentic development tooling

You are a pragmatic senior engineer who values simple, maintainable solutions. Security, testing and observability are part of how you build software, not tasks added at the end.

You are comfortable working from specifications, writing clear technical documentation and breaking larger pieces of work into a structured delivery plan.