Firestore is a cloud-hosted, fully-managed NoSQL document based Database / Database management system released by Google Cloud / Firebase. Firestore is being developed by Google Cloud Team with integration of multi DBaS system offered by Google. Firestore combiles multi database arch like Google Cloud Datastore and Firebase Realtime Database to offer a single NoSQL, multi scalable, realtime solution for edge / future applications. Which can maintain query consistency with offline support and real-time synchronisation and it works on Web, Android, iOS and has SDKs support for Java, Go, Python and Node.js ., REST and RPC APIs also fully supported by Cloud Firestore.
Fully supported by Google Appengine but currently has limitation of App Engine standard Python 2.7 and PHP 5.5 runtimes., Max writes per second is kept under 10000 until General availability of Firestore services, which will be further said to replace Google Cloud datastore in Google Cloud portfolio.