How to fix INVALID_ARGUMENT: Composite index is required for this query in Firebase

In the Firebase Console, navigate to Firestore Database > Indexes > Composite. The index configuration should be pre-filled with your collection name and field definitions. Review the fields and their sort order (Ascending/Descending), then click Create Index. Building the index typically takes a few minutes depending on your data size.

Wait for the index status to change from "Building" to "Enabled". You can monitor progress in the Composite Indexes tab. Once enabled, your query will execute successfully.

If you have multiple indexes to create, use the Firebase CLI:

firebase init firestore

This generates a firestore.indexes.json file in your project. Edit it to define all your composite indexes:

{
  "indexes": [
    {
      "collectionGroup": "posts",
      "queryScope": "Collection",
      "fields": [
        { "fieldPath": "status", "order": "ASCENDING" },
        { "fieldPath": "createdAt", "order": "DESCENDING" }
      ]
    }
  ]
}

Then deploy:

firebase deploy --only firestore:indexes

After the index is enabled, run your query again. It should now execute without the composite index error. If using the SDK, you do not need to change your code—Firestore will automatically use the new index.