By default, all accounts come with 2 calls per second per account. Outbound Call API requests are queued upon acceptance, then dequeued and initiated as per the Calls Per Second (CPS) configured for your Plivo account. To request for an increase in the number of calls you can make per second for your account, please send us a message at the Contact page or directly at sales(at)plivo.com. (Due to extra costs incurred by carriers and server providers, a minimum commitment is required, depending on the number of calls per second you request.)
For Inbound Calls, there is no limit on the number of inbound calls your number can receive per second: however, please note that, due to certain carrier restrictions, a majority of incoming calls on a single number must be answered and should not be used for services like missed call services.