APIs and integrations · Papendrecht

API integration and custom API development

VirtuoLab is a software agency in Papendrecht, the Netherlands, building API integrations and custom APIs with Node.js and TypeScript. VirtuoLab connects webshops, CRM systems such as HubSpot or Microsoft Dynamics, accounting software such as Exact Online, AFAS and SnelStart, and payment providers such as Mollie and Stripe. For example, a business running 2 sites on WooCommerce can send every paid order, with payment data from Mollie, straight to Exact Online, without retyping a single invoice. First comes a free intake call, then a fixed price upfront. In 2026, a simple integration costs €1,500 to €4,000. The client owns the code and the data after delivery.

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Price indication
€1,500 – €30,000 (simple integrations from €1,500)
Stack
Node.js, TypeScript, Python, PostgreSQL, GraphQL, Docker
Service area
On location in the Drechtsteden and Rotterdam; online across the Netherlands, Belgium and Germany
Contact
Directly with the developer
Ownership
Source code, documentation and data belong to the client

What is an API integration, and what does VirtuoLab build?

An API integration is a software link between two systems, so data moves automatically and nobody retypes figures by hand. VirtuoLab, a software agency in Papendrecht, builds API integrations as fixed-price projects. VirtuoLab connects webshops, CRM systems such as HubSpot or Microsoft Dynamics, accounting packages such as Exact Online, AFAS and SnelStart, and payment providers such as Mollie and Stripe. For example, a paid WooCommerce order can create an invoice in Exact Online and update the stock level straight away. VirtuoLab also builds custom REST and GraphQL APIs with Node.js, so a mobile app, a partner or a supplier can read data from one central system. Additionally, webhooks let a system react the moment something changes, instead of polling every 60 minutes. APIs are now the norm: 82% of organisations have adopted some level of an API-first approach, according to a survey by Postman in 2025. Every integration comes with logging, error handling and written documentation.

How much does an API integration cost?

An API integration from VirtuoLab is a fixed-price project with an indicative budget between €1,500 and €30,000 in 2026. First, a simple integration between two systems, such as WooCommerce and Exact Online, costs €1,500 to €4,000. Second, a custom REST API built with Node.js, including a data model, authentication and documentation, costs €5,000 to €15,000. Finally, a complex integration layer linking several systems, with queues, mapping rules and monitoring, costs €15,000 to €30,000. The price depends on the number of systems, the data volume, the business rules and the quality of each supplier's API documentation. Documentation is a real cost driver: 55% of respondents in the 2025 State of the API report by Postman struggle with inconsistent documentation. For example, matching customers between a CRM and AFAS takes extra work when both systems use different customer numbers. All amounts are indications. VirtuoLab sets the exact fixed price after a free intake call, once every endpoint and every data flow is on paper.

How long does an API integration take, and how does the project run?

The timeline of an API integration is a fixed part of the quote, because the duration depends mainly on the systems involved. VirtuoLab names no standard period in advance, since a link between two systems and a full integration layer differ too much. Every project in 2026 follows the same 4 steps. Step 1 is intake and scope, with VirtuoLab mapping the systems, the data flows and the access rights. Step 2 is design and validation, where the client approves the field mapping and the error scenarios. Step 3 is building and testing in short sprints, with a demo on test data after each sprint. Finally, step 4 is the launch, followed by support whenever a supplier changes an API. For example, connecting 2 sites to one Exact Online administration doubles the number of flows to test. In practice, getting an API key or a sandbox account from Exact or AFAS can take a while, so the quote lists such dependencies separately.

Which technology does VirtuoLab use for API integrations, and why?

The standard stack for a VirtuoLab integration is Node.js with TypeScript, because one typed language then covers the API, the webhooks and the background jobs. Python is the alternative when an integration needs heavy data processing or a library exists only for Python. PostgreSQL stores the mappings, the logs and a copy of each processed message, so every transaction stays traceable. PostgreSQL is also widely trusted: 55.6% of developers used PostgreSQL in the Stack Overflow Developer Survey 2025. Additionally, Docker packages the integration for AWS or an existing client server. For external partners, VirtuoLab builds REST for simple, predictable endpoints and GraphQL when a front end needs flexible queries. A queue retries failed calls instead of losing data. A Mollie webhook, for example, carries only the payment id, according to Mollie, and Mollie retries a webhook up to 10 times over 26 hours. The receiving system fetches the real status through the Mollie API, so a forged call can never mark an order as paid.

Why have VirtuoLab build your API integration?

VirtuoLab is a one-person software agency, so every integration is designed and coded by VirtuoLab itself. Clients talk directly with Mustafa Kose, the founder and developer, without an account manager in between. Three agreements apply to every project in 2026. First, the client receives a fixed price before any code is written. Second, each sprint ends with a demo on test data, so mapping errors surface early. Third, the client owns the source code, the documentation and the data after delivery. VirtuoLab is also honest when custom code is not the best choice. For example, a standard connector from the software supplier is sometimes cheaper for a single simple flow used by 3 people. The free intake call checks such options first. VirtuoLab is reachable Monday to Friday from 09:00 to 18:00. Meetings take place on location in the Drechtsteden and Rotterdam, or online for clients across the Netherlands, Belgium and Germany.

Which businesses is an API integration from VirtuoLab suitable for?

An API integration from VirtuoLab is suitable for small and medium-sized businesses whose staff retype data between systems every week. Typical cases are webshops built with WooCommerce or Shopify, wholesalers syncing stock with suppliers, and service companies whose CRM, such as Microsoft Dynamics, must feed AFAS or Exact Online. Additionally, a custom API suits a company planning a mobile app, a customer portal or a partner platform on top of existing data. Step 1 is a simple test: does someone enter the same order 2 times, once in the webshop and once in the accounting package? In practice, such double entry is the clearest sign an integration is worth a closer look. The service fits less well when one simple flow is enough and a ready-made connector already exists. VirtuoLab works on location for businesses in Papendrecht, Dordrecht, Zwijndrecht, Rotterdam and the rest of the Drechtsteden. Online, VirtuoLab serves companies across the Netherlands, Belgium and Germany, in Dutch, English or German.

Our own products

Software we build and run ourselves

FiscalDesk and Bouwklok are VirtuoLab products. Both are live and can be tried. The images below are recordings and screens from the software itself.

Accounting software for accounting firms

FiscalDesk

  • Reads and books invoices automatically
  • Only exceptions reach the accountant
  • App for clients to scan receipts
Next.jsReactPostgreSQLClaude (Anthropic)
View the projectfiscaldesk.nl

Frequently Asked Questions

How does VirtuoLab secure an API integration?

A secure API integration is an integration in which every request is authenticated, every object access is checked and no secret sits in the code. The top risk in the 2023 edition of the API Security Top 10 is broken object level authorization, according to OWASP. Put simply, a user changes an id in a request and sees another customer's data. In the web application list, 100% of the applications tested had some form of broken access control, ranked number 1 in the OWASP Top 10 of 2025. VirtuoLab therefore checks ownership on every object, not only at login. For example, a portal user only sees orders of the user's own company. Further measures are OAuth 2.0 or API keys, rate limiting, input validation and HTTPS. Secrets live in environment variables or a secrets manager, never in Git. Incoming webhooks are verified first, by checking a signature or by fetching the status via Mollie. Finally, logs record which system changed which record and when, without storing passwords.

What is the difference between REST, GraphQL and webhooks?

REST is an API style in which each URL represents a resource, such as an order or a customer. Standard HTTP methods then read, create or change the resource. GraphQL is a query language for APIs: the client asks for exactly the fields needed, in a single request. A webhook works the other way round: the source system sends a message the moment an event happens, such as a paid invoice. First, REST remains the foundation: Postman counted 93% for REST in the State of the API report of 2025. Second, webhooks reach 50% and GraphQL 33% in the same Postman report. Most integrations combine all three, each for a different job. For example, a shop built with WooCommerce receives a webhook from Mollie and then fetches the payment details through the Mollie API. VirtuoLab builds both API styles in Node.js and TypeScript. The choice is made per connection, based on what the other system supports and how much data moves each day.

What happens when Exact Online or another supplier changes its API?

An API change is a normal event in the life of an integration, because suppliers release new versions and retire old endpoints. Shopify, for example, marked the REST Admin API as legacy on 1 October 2024. Since April 2025, Shopify requires every new public app to work with GraphQL through the GraphQL Admin API. Versioning is far from universal: only 60% of respondents version their APIs, according to the State of the API report (Postman 2025). First, VirtuoLab keeps the code for each supplier in a separate module, so a change touches one part instead of the whole integration. Second, automated tests on the field mapping quickly show whether a new version breaks an order, an invoice or a stock update. After launch, the client chooses between updates on request and ongoing support. Because the client owns the code, another developer can also take over later. VirtuoLab documents every data flow, the field mapping and the error handling with such a handover in mind.

Can VirtuoLab connect software without a public API?

A system without a public API can often still be connected, but the route is less direct. The first option is a scheduled export: many packages can write a CSV or XML file, for example once a night or 4 times a day, which the integration collects via SFTP or through Google Drive. The second option is a read-only database connection, when the supplier and the licence allow one. The third option is asking the supplier for partner access, because some APIs are only available on request. Screen scraping is a last resort, since a small layout change breaks the link. In practice, the chosen route decides a large part of the budget. A nightly CSV import from an older ERP system costs less than a real-time link, for example an export every night at 02:00. The trade-off is data up to a day old. The free intake call from VirtuoLab compares the options, before any price is set.

Is a tool such as Zapier or Make cheaper than a custom integration?

A no-code tool such as Zapier or Make is often the faster and cheaper choice for one simple flow, and VirtuoLab says so during the intake. For example, a website form entry going straight into a CRM is a typical job to build with Zapier. Custom code becomes the better choice in three situations. First, the business rules get complex. Second, records need matching and validation across systems. Third, volumes grow, for example a nightly sync of 5,000 customers, and every failed run needs a reliable retry. Ownership matters too. No-code platforms charge a recurring subscription, and the logic lives on the platform of the supplier. In 2026, a custom integration from VirtuoLab has hosting costs plus a one-off fixed price from €1,500. The client owns the code and can move the integration to another server or another developer. VirtuoLab compares both routes in the free intake call, before any quote is made.