The performance efficiency of the service is key to assessing the quality of the service. Performance requirements to be agreed between all interested parties cover the capacity of the service and its response times.
The capacity of the service, i.e. the expected maximum rate at which the service can process transactions and the maximum message size of responses must be specified. The requirement can include the number of items that can be stored, the number of concurrent users, the communication bandwidth, throughput of transactions, and size of messages.
The expected time bahaviour of the service, i.e. the processing/response time, must be specified. This can be expressed as an indication of a maximum time needed for the service provider to complete the request, measured from the time instant the service provider receives the request to the time instant the service provider sends the response or makes it available.