firebase-firestore-basics

name	firebase-firestore-basics
description	Comprehensive Firestore skill covering provisioning, security rules, SDK usage, query mechanics, aggregation, and indexing. Use when writing Firestore queries, security rules, or setting up Firestore.
compatibility	Best used with Firebase CLI (`npm install -g firebase-tools`). Supports Standard and Enterprise editions.

Firestore Basics

Complete guide for Cloud Firestore — provisioning, securing, querying, and optimizing.

Edition Awareness (Check First)

Before writing ANY Firestore code, determine the edition:

• Standard: Classic rules + limits. Most projects use this.
• Enterprise (Pipeline): 100+ features — groupBy, min/max, countDistinct, optional indexes, query.explain(). Available since Jan 2026.

Agent MUST NOT suggest Pipeline syntax for Standard projects — it will error.

Provisioning

Set up Cloud Firestore in your Firebase project and local environment: provisioning.md

Security Rules

Write and deploy Firestore Security Rules to protect your data: security_rules.md

SDK Usage

CRUD operations, real-time listeners, queries, aggregation, pagination: web_sdk_usage.md

Query Mechanics (Deep Dive)

How Firestore processes queries internally — execution model, index selection, cost model, aggregation mechanics, and the agent pre-query checklist: query_mechanics.md

Indexes

Index types, composite index ordering rules, Enterprise differences, and management: indexes.md

Agent Pre-Query Checklist

Before generating ANY Firestore query:

1. Edition? → Standard or Enterprise? Determines available syntax.
2. Aggregation? → getAggregateFromServer (Standard) or db.pipeline().aggregate() (Enterprise). NEVER client-side reduce/sum/count.
3. Compound query? → Composite index needed? Field order: equality → inequality → orderBy.
4. OR / in? → Disjunction count ≤ 30.
5. Index exists? → Standard: error + create link. Enterprise: warn about scan cost.
6. Pagination? → Cursor-based only (startAfter). No offset.
7. Real-time? → Cannot use Pipeline syntax. Use Core query.
8. Explain? → Use query.explain() on Enterprise to verify planner decisions.