ExtServices is an updatable Mainline module that contains the logic used by Android framework components such as storage cache, autofill, textclassifier, package watchdog, notifications and notification ranking that run continually. For the new features or bug fixes of these platform defined services above or a new added platform service, it will provide more flexibility and benefits by updating ExtServices in a more frequent cycle than a platform release cycle.
Before you start to develop on ExtServices, please read go/smart-os-extservices to get the guideline.