Cloud Firestore is a fast, fully managed, serverless, cloud-native NoSQL document database that simplifies storing, syncing, and querying data for your mobile, web, and IoT apps at global scale. Its client libraries provide live synchronization and offline support, while its security features and integrations with Firebase and Google Cloud Platform (GCP) accelerate building truly serverless apps. (Definition from https://cloud.google.com/firestore/)
src/app/firebase/firebase-listing/firebase-listing.page.tsperforms both filters at the same time.
searchUsersByAge(lower: number, upper: number): Observable<FirebaseListingModel>method in