diff --git a/main.tf b/main.tf
index aeae319..bdecc6c 100644
--- a/main.tf
+++ b/main.tf
@@ -50,30 +50,31 @@ resource "google_spanner_instance" "instance_num_node" {
   config       = var.instance_config
   display_name = var.instance_display_name
   name         = var.instance_name
-  num_nodes    = var.instance_size.num_nodes
+  num_nodes    = var.enable_autoscaling ? null : var.instance_size.num_nodes
   labels       = var.instance_labels
 
   dynamic "autoscaling_config" {
     for_each = var.enable_autoscaling ? [1] : []
     content {
       autoscaling_limits {
-        min_processing_units = var.min_processing_units
-        max_processing_units = var.max_processing_units
-        min_nodes            = var.min_nodes
-        max_nodes            = var.max_nodes
+        min_nodes = var.min_nodes
+        max_nodes = var.max_nodes
       }
       autoscaling_targets {
         high_priority_cpu_utilization_percent = var.high_priority_cpu_utilization_percent
         storage_utilization_percent           = var.storage_utilization_percent
       }
-      asymmetric_autoscaling_options {
-        replica_selection {
-          location = var.replica_location
-        }
-        overrides {
-          autoscaling_limits {
-            min_nodes = var.override_min_nodes
-            max_nodes = var.override_max_nodes
+      dynamic "asymmetric_autoscaling_options" {
+        for_each = var.enable_asymmetric_autoscaling ? [1] : []
+        content {
+          replica_selection {
+            location = var.replica_location
+          }
+          overrides {
+            autoscaling_limits {
+              min_nodes = var.override_min_nodes
+              max_nodes = var.override_max_nodes
+            }
           }
         }
       }
@@ -93,6 +94,8 @@ resource "google_spanner_instance" "instance_processing_units" {
   name             = var.instance_name
   processing_units = var.instance_size.processing_units
   labels           = var.instance_labels
+  edition          = var.edition
+  force_destroy    = var.force_destroy
 }
 
 data "google_spanner_instance" "instance" {
diff --git a/variables.tf b/variables.tf
index 375b0af..c194db3 100644
--- a/variables.tf
+++ b/variables.tf
@@ -41,14 +41,7 @@ variable "instance_size" {
     num_nodes        = optional(number)
     processing_units = optional(number)
   })
-  validation {
-    condition = !(
-      try(var.instance_size.num_nodes, null) == null
-      &&
-      try(var.instance_size.processing_units, null) == null
-    )
-    error_message = "Either num_nodes OR processing_units information is supported."
-  }
+  default = null
 }
 
 variable "create_instance" {
@@ -63,6 +56,12 @@ variable "enable_autoscaling" {
   default     = false
 }
 
+variable "enable_asymmetric_autoscaling" {
+  description = "Enable asymmetric autoscaling for the Spanner Instance"
+  type        = bool
+  default     = false
+}
+
 variable "instance_iam" {
   description = "The list of permissions on spanner instance"
   type        = list(string)