For inbound calls, given this is something that wen can't control, say we have the ability to handle 50 concurrent calls on our plan. If the 51st concurrent call rings the number, rather than just dropping the call, is it possible that there could be a soft cap until the next month, or some kind of call queue etc? Essentially, we don't want to have to overprovision for concurrent calls to handle a huge spike, but would like to be able to handle spikes with either a call queue or a chance to pay for that overage etc rather than having calls be dropped.

You can upgrade your limit via billing, but there's no built-in queuing. To handle spikes, you'd need to queue calls yourself (e.g. using Twilio before handing off to VAPI).

VAPI doesn’t support call queuing or soft caps once your 50 concurrent call limit is reached, new calls are dropped unless you implement a queue with Twilio or upgrade your plan to handle more concurrency...

Thanks, are there any docs on how to implement a call queue with twilio and vapi?