What is an API?
An API (Application Programming Interface) is a bridge between two software systems. It lets applications communicate with each other and exchange data.
Why APIs matter for your business
Connect systems — link your webshop to your accounting software
Automate — let systems synchronise data automatically
Scalability — build modular systems that can grow independently
Time to market — use existing services instead of building everything yourself
Types of API
REST API — the standard. Uses HTTP methods (GET, POST, PUT, DELETE). Ideal for most applications.
GraphQL — more flexible than REST. The client decides exactly which data it requests. Ideal for complex, data-heavy apps.
WebSocket — for real-time communication. Chat, live updates, gaming.
Webhook — event-driven. System B is automatically notified when something changes in system A.
Common API integrations
| Category | Examples |
|---|---|
| Payments | Mollie, Stripe, PayPal |
| Accounting | Exact Online, Moneybird, Xero |
| Mailchimp, SendGrid, Postmark | |
| CRM | Salesforce, HubSpot, Pipedrive |
| Shipping | PostNL, DHL, SendCloud |
| Social media | Meta, LinkedIn, X API |
The cost of API development
| Type | Cost |
|---|---|
| Simple API connection | €1,500 – €4,000 |
| Custom REST API | €5,000 – €15,000 |
| Complex integration layer | €15,000 – €30,000 |
How we build APIs
At VirtuoLab we build robust, documented APIs with Node.js, Python or Go. We follow best practices for security (OAuth 2.0, rate limiting, input validation) and provide thorough documentation.