Any user can be designated as concurrent web services user if one or more SuiteCloud Plus license has been purchased.
Generally, you can purchase one SuiteCloud Plus license per NetSuite account. Contact your sales representative to discuss any need for additional licenses.
Web services and RESTlet concurrency is also governed per account. The new account governance limit applies to the combined total of web services and RESTlet requests. Due to this change, if a designated user makes 10 concurrent web services requests, the number of successful requests depends on other web services or REST requests that are being processed. Each SuiteCloud Plus license increases the account base limit for concurrent web services requests by 10. The account base limit depends on your service tier.