Sending messages at scale can be complex, especially across many countries, but Twilio has resources and tools available to make it easier for you. One of these key features is Messaging Services, which lets you assemble a pool of Twilio numbers and other sender types, and leverage Twilio's intelligence to make number selection easier.
If you are learning about Messaging Services for the first time, check out Getting started with Messaging Services for an introduction.
If you are preparing to grow your messaging use case, Twilio has published updated guidance on operating at-scale with a Messaging Service, including use case considerations and number selection. Please refer to Best Practices for Scaling with Messaging Services for details.