How to restrict access to a forms API?

I have a form created on HubSpot which I would like to restrict access to.

The data for this form is sent from a client web application to a backend server, which creates its own database record before forwarding this data to the HubSpot forms API.

Because the form data is submitted programmatically, we have disabled CAPTCHAs. Ideally, this form should not be publicly POSTable so as to prevent any client except for the server from triggering HubSpot emails and workflows.

I’d like to restrict access to this API to only users with an API key, that way only the server process and other developers can hit it directly.

@06047

Would this endpoint be what you are looking for? HAPIKEY is required for submission