12 Verticals, 1 Platform: The HetPlein Architecture

The challenge: 12 industries, one codebase

When we started building HetPlein, we knew it would serve multiple industries. What we didn't know was how different those industries would be. A homeowner looking for a plumber has fundamentally different needs than a business looking for an accountant. The intake questions differ. The matching criteria differ. The trust signals differ. Even the urgency differs.

We had a choice: build 12 separate marketplaces, or build one platform that's flexible enough to serve them all. We chose the latter — and it turned out to be the most consequential architectural decision we've made.

Multi-tenant architecture, marketplace edition

HetPlein runs on a multi-tenant architecture where each vertical (Klusplein, Boekhoudplein, Bouwplein, etc.) is a tenant with its own:

• Database. Complete data isolation. A plumber on Klusplein can't see an accountant's data on Boekhoudplein. This isn't just security — it's regulatory compliance for sectors like legal and healthcare.
• Branding. Each vertical has its own domain, colour scheme, logo, and visual identity. Klusplein.eu looks and feels different from Tandartsenplein.eu, even though they share the same engine.
• Configuration. Intake wizards, matching algorithms, review criteria, and notification flows are all configurable per tenant. No code changes needed to launch a new vertical.

But they share:

• Core platform code. One codebase, one deployment pipeline, one monitoring stack. A security fix or performance improvement benefits all 12 verticals simultaneously.
• Infrastructure. Kubernetes orchestration, PostgreSQL databases, Redis caching, SeaweedFS storage — all shared, all EU-hosted.
• Operational processes. One team operates all verticals. Knowledge gained from running Klusplein informs how we operate Rechtplein.

What we learned in production

After operating 12 verticals simultaneously, here are the lessons that surprised us:

1. Intake design matters more than matching algorithms

We spent weeks on our matching algorithm. It's good. But the biggest impact on match quality came from redesigning the intake wizard. When customers describe their needs more precisely, even a simple matching algorithm produces great results. The intelligence is in the questions, not the algorithm.

2. Trust signals are industry-specific

On Klusplein, customers want to see photos of previous work. On Boekhoudplein, they want to see certifications and years of experience. On Tandartsenplein, they want insurance acceptance and location proximity. We built a flexible trust-signal system that each vertical configures independently.

3. Database-per-tenant is worth the operational cost

We debated schema-based isolation vs. database-per-tenant for months. Database-per-tenant is operationally harder — more connections, more migration management, more backup complexity. But it's the right choice for a marketplace handling sensitive professional data across regulated industries. The isolation guarantees are worth every minute of extra ops work.

4. The 13th vertical is trivially easy

Launching the first vertical took months. The second took weeks. By the fifth, we had a repeatable process: configure the tenant, customise the intake wizard, set up branding, seed the initial professional database, and launch. The platform engineering investment pays compound returns.

The numbers

Today, HetPlein serves over 60,000 platform users across 12 verticals. The entire system runs on a Kubernetes cluster hosted in the EU, with automated deployments multiple times per week. Average uptime is above 99.9%.

And because we operate it ourselves, we know exactly where the bottlenecks are, which queries need optimisation, and which features drive engagement. This operational data is what makes the platform better every week — not a product roadmap in a slide deck, but real usage patterns from real customers.

What this means for your industry

If you're an industry association, a franchise network, or a business that wants to build a vertical marketplace — you don't need to start from zero. The platform engine that powers HetPlein can be adapted for your industry in weeks, not years. Custom intake, custom matching, custom branding — but battle-tested infrastructure underneath.

That's the advantage of building and operating your own platform: every new vertical builds on everything that came before it.