Firestore V2

Cloud Firestore is Google's scalable NoSQL document database — deeply integrated with Firebase (mobile/web) and available as a standalone GCP service. For agents: the Python Admin SDK enables full CRUD operations, batch writes, and transactions server-side. The data model (collections → documents → subcollections) maps well to hierarchical data. Real-time listeners are primarily for client-side use; agents typically use one-time reads and batch writes. Free tier (50K reads/day, 20K writes/day) is generous for development. ACID transactions and batch writes for data consistency. Confidence is docs-derived.

Firebase Admin SDK (Python): db = firestore.Client(project=project_id, credentials=credentials). db.collection("users").add({name: "Alice", email: "alice@example.com"}) creates document (auto-ID). db.collection("users").document(doc_id).set({...}) creates/replaces with known ID. db.collection("users").document(doc_id).update({field: value}) updates fields. db.collection("users").document(doc_id).get() retrieves document. db.collection("users").where("age", ">=", 18).stream() queries collection. db.collection("users").document(doc_id).delete() deletes. Batch writes: batch = db.batch(); batch.set(ref, data); batch.commit(). Transactions: db.transaction() for atomic multi-document reads/writes. REST API: projects.databases.documents.* namespace.

Service Account auth (recommended for agents): google.oauth2.service_account.Credentials or Application Default Credentials (ADC). Firebase Admin SDK initializes with credentials automatically. HTTPS enforced. Firebase Security Rules: for client-side SDKs (not applicable for Admin SDK — Admin SDK bypasses rules). Google Cloud IAM: roles/datastore.user for Firestore access. No OAuth2 for Admin SDK. Client SDK (Web/Mobile): authenticated via Firebase Authentication user tokens.

Standard errors via SDK exceptions (google.cloud.exceptions.NotFound, etc.). 409 for transaction contention (retry automatically in SDK). Write limits: 1 write/sec per document (shard for high-frequency counters). Batch writes: max 500 operations per batch. Index: composite indexes required for multi-field queries — create via Firebase Console or Terraform. Firestore uptime at status.firebase.google.com. Query limitations: no JOIN, no full-text search (use Algolia/Typesense for search). Transaction retries: Firestore SDK retries contended transactions automatically (5 retries by default).

firebase.google.com/docs/firestore covers Firebase Admin SDK guide (Python, Node.js, Go, Java, .NET), REST API reference, security rules documentation, and performance guide. Getting started: GCP/Firebase project (free), enable Firestore, install firebase-admin — first document in under 5 minutes. firebase-admin: pip install firebase-admin. Terraform: google_firestore_document. Community via Firebase community and Stack Overflow (google-cloud-firestore tag). Excellent documentation with clear examples; Firebase ecosystem resources are extensive.