Use push notifications to receive updates from resources, instead of actively querying resources (i.e., polling).
Mobile apps need to get updates from resources (e.g., from server). One way of checking for updates is by periodically query those resources. However, this will lead to several requests that will return no update, leading to unnecessary energy consumption.
Use push notifications to get updates from resources. Note -- this is a big challenge amongst FOSS apps since there is no good open source alternative for Firebase Cloud Messaging (former Google Cloud Messaging).
In a messaging app, instead of actively check for new messages, the app can subscribe push notifications.