How to fix Error: Error creating Firestore Database: AlreadyExists in Terraform

The most straightforward solution is to import the existing database into your Terraform state. This tells Terraform that it now manages the existing resource.

First, find your GCP project ID and determine the database name (usually "(default)" for the default database):

# List all Firestore databases in your project
gcloud firestore databases list --project=MY_PROJECT_ID

Then, import the database into your Terraform state:

terraform import google_firestore_database.default projects/MY_PROJECT_ID/databases/(default)

If you have a differently named database resource in your Terraform config, adjust accordingly:

terraform import google_firestore_database.my_database projects/MY_PROJECT_ID/databases/my-database-name

After importing, verify the state was updated:

terraform state show google_firestore_database.default

Now terraform plan and apply should work without trying to recreate the database.

If the database was created as a side effect of enabling google_app_engine_application, explicitly manage the dependency order in Terraform:

resource "google_project_service" "firestore" {
  service            = "firestore.googleapis.com"
  disable_on_destroy = false
}

resource "google_app_engine_application" "app" {
  depends_on = [google_project_service.firestore]

  project    = var.gcp_project_id
  location_id = "us-central"
  database_type = "CLOUD_FIRESTORE"
}

# This may conflict, so import the existing database instead
# resource "google_firestore_database" "default" {
#   project = var.gcp_project_id
#   name = "(default)"
#   location_id = "us-central"
#   type = "FIRESTORE_NATIVE"
# }

By declaring google_project_service.firestore and using depends_on, you control when Firestore is enabled. However, App Engine may still auto-create the database, so importing (Step 1) is still the recommended approach.

Before importing, confirm the database exists and note its properties:

# Get detailed information about the default database
gcloud firestore databases describe --database=(default) --project=MY_PROJECT_ID

This shows:
- Database name (usually "(default)")
- Location (e.g., "us-central1")
- Type (e.g., "FIRESTORE_NATIVE" or "DATASTORE_MODE")
- Current status

Example output:

name: projects/my-project/databases/(default)
location: us-central1
type: FIRESTORE_NATIVE
createTime: '2023-01-15T10:30:00Z'

Make sure your Terraform configuration matches these settings when you import the database.

If you have a google_firestore_database resource block in your Terraform configuration that conflicts with the existing database, you have two options:

Option A: Comment it out temporarily (for import)

# resource "google_firestore_database" "default" {
#   project = var.gcp_project_id
#   name = "(default)"
#   location_id = "us-central"
#   type = "FIRESTORE_NATIVE"
# }

Run terraform import (Step 1), then uncomment it. The import command creates a matching state entry so the resource declaration matches the state.

Option B: Delete and recreate (advanced)

If you're in development and can afford downtime:

# Delete the database in GCP
gcloud firestore databases delete --database=(default) --project=MY_PROJECT_ID

# Now terraform apply will create it fresh
terraform apply

Warning: Deleting a Firestore database is irreversible and deletes all data. Only use this in development environments.

If you prefer not to manage the Firestore database with Terraform, use a data source to reference the existing database:

# Reference the existing database without managing it
data "google_firestore_database" "default" {
  project  = var.gcp_project_id
  database = "(default)"
}

output "firestore_database" {
  value = data.google_firestore_database.default
}

This approach:
- Reads the database properties from GCP
- Does NOT try to create or modify the database
- Allows you to reference it in other resources (e.g., indexes, security rules)
- Is useful when the database lifecycle is managed outside of Terraform

This is ideal if the database is shared across multiple Terraform configurations or managed by a different team.

If you're using both google_app_engine_application and google_firestore_database, the order matters:

resource "google_project_service" "appengine" {
  service            = "appengine.googleapis.com"
  disable_on_destroy = false
}

resource "google_project_service" "firestore" {
  service            = "firestore.googleapis.com"
  disable_on_destroy = false
}

resource "google_app_engine_application" "app" {
  depends_on = [
    google_project_service.appengine,
    google_project_service.firestore,
  ]

  project      = var.gcp_project_id
  location_id  = "us-central"
  database_type = "CLOUD_FIRESTORE"
}

# Import existing database instead of creating
# Or use data source (see Step 5)

Important note: Even with proper depends_on, the App Engine application may auto-create the Firestore database as a side effect. The import approach (Step 1) is the most reliable fix.