New features of AWS IoT Core, including Configurable Endpoints and Custom Domains, as well as enhancement to AWS IoT Core Custom Authentication, Custom Authorizer for MQTT Connections, make it easy to transition from self-managed infrastructure to fully managed AWS IoT services so you can improve scalability and reliability with few changes to your application code and minimal to no impact to devices already using your services. 

from Recent Announcements: https://aws.amazon.com/about-aws/whats-new/2019/11/aws-iot-core-makes-it-easier-to-transform-from-self-managed-to-fully-managed-aws-iot-services/