This serverless system is designed to call Twilio's APIs at a metered rate, handling issues such as rate limiting, monitoring and reporting, and error handling. It uses Amazon AWS serverless technologies like Lambda, Step Functions, SQS, SNS, and S3, along with managed products, to build an Infrastructure as Code (IaC) solution that can be easily deployed into any AWS account. The system allows for the processing of large batches of API calls from CSV or JSON files, rate-limiting calls to avoid exceeding Twilio's concurrency limits, and reporting and monitoring capabilities using Twilio Insights. It also includes downstream processors to intelligently process feedback from Twilio, such as saving responses to S3 or DynamoDB, checking for errors, and handling 429 errors by retrying API calls. The system is designed to be customizable, scalable, and cost-effective, making it suitable for a variety of use cases, including large-scale applications and proof-of-concepts.