What is Cloud Firestore?

Cloud Firestore is GCP's flexible, scalable NoSQL document database. It stores data in documents (JSON-like objects with fields) organized in collections. Key features: Real-time listeners: clients subscribe to documents/collections and receive updates in real time — ideal for mobile and web apps. Offline support: client SDKs cache data locally, enabling offline functionality. Strong consistency: unlike many NoSQL databases. Automatic scaling: from 1 to 1M+ operations/second. ACID transactions: multi-document. Security Rules: define access control that runs close to the data. Two modes: Native mode (recommended) and Datastore mode (backward compatible with old Cloud Datastore). Firestore is the primary database for Firebase applications.