Our system needs to process PDF invoice files from generic external third parties.

Using HTTP is the most obvious, but this isn't the greatest of ideas in case we need to deal with bulk uploads.
Even when we push all HTTP requests on a queue behind the http controller, when thousands of PDF's are sent to the server as a batch process by different clients, I feel this will be too much.

It makes more sense to expose a queueing system (like amqp, since we will use RabbitMq internally), but our clients should be generic, and we can't impose the necessity of implementing amqp to our clients. It isn't as omnipresent as HTTP clients.

Is there a third option you could advise that I'm currently not seeing?

Our system needs to process PDF invoice files from generic external third parties.

Using HTTP is the most obvious, but this isn't the greatest of ideas in case we need to deal with bulk uploads.
Even when we push all HTTP requests on a queue behind the http controller, when thousands of PDF's are sent to the server as a batch process by different clients, I feel this will be too much. (Edit: we may at least initially solve this with rate limiting as it concerns as startup idea).

It makes more sense to expose a queueing system (like amqp, since we will use RabbitMq internally), but our clients should be generic, and we can't impose the necessity of implementing amqp to our clients. It isn't as omnipresent as HTTP clients.

Is there a third option you could advise that I'm currently not seeing?