diff --git a/README.md b/README.md
index 653ad1a..5af2d1e 100644
--- a/README.md
+++ b/README.md
@@ -49,9 +49,9 @@ In order to run all checks at any point run the following command:
 
 | Name | Source | Version |
 |------|--------|---------|
-| <a name="module_acm"></a> [acm](#module\_acm) | terraform-aws-modules/acm/aws | ~> 3.0 |
+| <a name="module_acm"></a> [acm](#module\_acm) | terraform-aws-modules/acm/aws | ~> 4.0 |
 | <a name="module_aws_cw_logs"></a> [aws\_cw\_logs](#module\_aws\_cw\_logs) | cn-terraform/cloudwatch-logs/aws | 1.0.10 |
-| <a name="module_ecs_fargate"></a> [ecs\_fargate](#module\_ecs\_fargate) | cn-terraform/ecs-fargate/aws | 2.0.39 |
+| <a name="module_ecs_fargate"></a> [ecs\_fargate](#module\_ecs\_fargate) | cn-terraform/ecs-fargate/aws | 2.0.42 |
 
 ## Resources
 
@@ -69,7 +69,6 @@ In order to run all checks at any point run the following command:
 
 | Name | Description | Type | Default | Required |
 |------|-------------|------|---------|:--------:|
-| <a name="input_availability_zones"></a> [availability\_zones](#input\_availability\_zones) | List of Availability Zones | `list(string)` | n/a | yes |
 | <a name="input_block_s3_bucket_public_access"></a> [block\_s3\_bucket\_public\_access](#input\_block\_s3\_bucket\_public\_access) | (Optional) If true, public access to the S3 bucket will be blocked. | `bool` | `true` | no |
 | <a name="input_db_engine_version"></a> [db\_engine\_version](#input\_db\_engine\_version) | DB engine version | `string` | `"14.2"` | no |
 | <a name="input_db_instance_size"></a> [db\_instance\_size](#input\_db\_instance\_size) | DB instance size | `string` | `"db.r4.large"` | no |
diff --git a/database.tf b/database.tf
index 48ecf8f..7b54802 100644
--- a/database.tf
+++ b/database.tf
@@ -60,7 +60,7 @@ resource "aws_rds_cluster" "aurora_db" {
 # AWS RDS Aurora Cluster Instances
 #------------------------------------------------------------------------------
 resource "aws_rds_cluster_instance" "aurora_db_cluster_instances" {
-  count                = length(var.availability_zones)
+  count                = length(var.private_subnets_ids)
   identifier           = "aurora-db-instance-${count.index}"
   cluster_identifier   = aws_rds_cluster.aurora_db.id
   db_subnet_group_name = aws_db_subnet_group.aurora_db_subnet_group.id