Integrations & Infrastructure

API Development that connects systems

We design and build REST and GraphQL APIs that perform under load, connect to any system and are documented down to the last detail. From the first endpoint definition to a production deployment with monitoring.

Our process

Quality assurance

Only live when every detail is right.

qa.ontwikkelaars.nl

Test overview

Status of all test categories.

Functional tests42/42
Integration tests18/18
User tests8/10
Regression tests31/31
99 of 101 tests passed

What we build

REST, GraphQL and real-time APIs

From simple CRUD endpoints to event-driven architectures — we build APIs that are scalable, well-secured and easy to integrate for other teams.

  • 01RESTful APIs with OpenAPI spec and interactive docs
  • 02GraphQL for flexible and efficient queries
  • 03WebSockets for real-time data and live dashboards
  • 04Webhook integrations with retry and signature verification

Project environment

Real-time insight into your project — anytime, anywhere.

app.ontwikkelaars.nl

Project overview

Daily summary of your project.

Project progress
87%
Sprint 4 of 5 completed
24Open tasks
Week 7Current sprint

Security & performance

Built for scale and security

Security and performance are not afterthoughts — they're baked into every endpoint. Your API is ready for production load from day one.

  • 01OAuth2/JWT authentication with PKCE
  • 02Rate limiting & throttling per plan
  • 03Automatic API documentation via Scalar
  • 04Versioning & backwards compatibility

Discovery

Everything mapped out — before the first sprint.

intake.ontwikkelaars.nl

Intake meeting

Getting to know your organisation and requirements.

Business goals and vision
Target audience and users
Technical requirements
Budget and timeline
Existing systems

Integrations & management

Connect everything that can be connected

We connect your systems with the tools you already use — from payment providers to ERP systems. And after go-live we keep a close eye on everything.

  • 01Payment providers (Stripe, Mollie)
  • 02Custom ERP/CRM integrations
  • 03Third-party SaaS APIs and webhooks
  • 04Monitoring, alerting and uptime guarantee

Management & growth

Your product grows — we stay on board.

beheer.ontwikkelaars.nl

Maintenance & updates

Proactive management of your platform.

Security updatesDone
Database back-upDone
Performance checkPlanned
Feature: search filterIn development
Case study

API layer for payment provider with 99.9% uptime

A payment provider asked us to replace their monolithic backend with a modern API layer. Result: 200+ endpoints, 99.9% uptime SLA and an average response time under 80ms.

200+

endpoints

99.9%

uptime

<80ms

response

APIs that make other teams happy

API-first development

We design the API before we write code. The OpenAPI contract leads — so frontend, mobile and external partners know exactly what to expect, before the first endpoint goes live.

Documentation that actually works

Our documentation is not an afterthought. We generate interactive API docs directly from the codebase, with real examples, error schemas and a sandbox for developers to test.

Monitoring & early warnings

After go-live you keep your finger on the pulse: uptime checks, p95 response time alerting, error rate dashboards and automatic notifications for anomalies. Issues are solved before customers notice them.

Everything you want to know about API development

REST is the better choice for simple CRUD operations, public APIs and scenarios where caching is crucial. GraphQL shines when multiple clients (web, mobile, partners) need the same data in different ways and you want to avoid over-fetching. We advise after the intake call on what fits best.

By default we implement OAuth2 with PKCE for interactive clients and client credentials for machine-to-machine. All endpoints run over HTTPS with HSTS, input validation prevents injection attacks, and rate limiting protects against brute-force and DDoS. Sensitive data is stored encrypted.

Absolutely. We regularly do API audits, add endpoints to existing services and migrate monolithic backends to a cleaner API layer. We always start with a technical audit so we know exactly what's there.

Our REST APIs typically run with a p99 response time under 200ms for simple CRUD operations. Through connection pooling, query optimisation, Redis caching and CDN strategies for static data, we achieve consistent performance even under high load.

We apply an explicit versioning strategy (e.g. /v1/, /v2/) and strictly maintain backwards compatibility. Breaking changes are communicated well in advance via changelogs and deprecation notices. Multiple versions can run concurrently so existing integrations don't break on upgrade.

We standardise error responses based on RFC 7807 (Problem Details for HTTP APIs) so error codes are consistent and readable for all consumers. Logs are centralised via an observability stack (e.g. Datadog, Grafana Loki) and we instrument all endpoints with distributed tracing for fast diagnosis in production.

Let's discuss your project

Schedule a free intro call. We discuss your needs and advise on the best approach.