TIL you can bypass ActiveCampaign's per-contact fee with a clever webhook setup

I've been evaluating ActiveCampaign's pricing model for a client, and the per-contact fee remains a significant cost driver, especially for large, low-engagement lists. The common advice is to delete or archive inactive contacts, but that destroys historical data.

A more elegant solution leverages their webhook system. The core idea is to maintain a master list *outside* ActiveCampaign (e.g., in a cloud database like Supabase or Airtable) and only sync active, engaged contacts into ActiveCampaign via real-time webhooks. This keeps the paid contact count minimal while preserving full data externally.

Here's a simplified architecture:

1. **External Database:** Holds your complete contact list with all fields and a status (e.g., `active`, `inactive`).
2. **Webhook Endpoint (AC -> Your Server):** Captures all contact activities (opens, clicks, form submissions).
3. **Logic Layer:** Updates the external database upon receiving webhooks. When a contact meets "active" criteria (e.g., opens an email), it triggers the sync *into* ActiveCampaign.
4. **Sync Mechanism (Your Server -> AC):** Uses ActiveCampaign's API to create or update the contact, ensuring they exist in the paid list only when necessary.

The key is the conditional creation logic. Your server should check if an inbound webhook's contact is already in ActiveCampaign before creating them. A basic implementation outline:

```javascript
// Pseudo-code for handling an 'email_open' webhook
app.post('/ac-webhook', async (req, res) => {
const { contact } = req.body;
const externalContact = await db.findContact(contact.email);

// Your business logic for "active" status
if (emailOpenCount > threshold) {
externalContact.status = 'active';
// Sync to ActiveCampaign only if not already present
const acContact = await acApi.findContactByEmail(contact.email);
if (!acContact) {
await acApi.createContact(externalContact);
}
}
await db.saveContact(externalContact);
res.sendStatus(200);
});
```

**Considerations & Gaps:**

* This adds complexity and requires a dedicated external server.
* You'll miss out on ActiveCampaign's built-in automation triggers for contacts who are not currently synced.
* Historical activity for inactive contacts resides solely in your system, not in AC's contact timeline.
* API rate limits and webhook reliability become your responsibility.

Has anyone implemented a production version of this? I'm particularly interested in observed pitfalls regarding:
* Handling contact merges or updates from multiple sources
* Maintaining tag consistency between systems
* The actual cost savings vs. development/maintenance overhead