diff --git a/backend/src/terraform/awsSubnet.ts b/backend/src/terraform/awsSubnet.ts
index 443c9ab..7b8d680 100644
--- a/backend/src/terraform/awsSubnet.ts
+++ b/backend/src/terraform/awsSubnet.ts
@@ -1,11 +1,12 @@
 import {jsonRoot} from "./util";
 import {Resource} from "./resource";
+import {awsZone, char} from "../types/terraform";
 
 export interface AwsSubnet {
 	vpc: string;
 	cidr_block: string;
 	map_public_ip_on_launch: boolean;
-	availability_zone: string;
+	availability_zone: `${awsZone}${char}`;
 }
 
 export class AwsSubnet extends Resource<AwsSubnet> implements AwsSubnet {
@@ -14,7 +15,7 @@ export class AwsSubnet extends Resource<AwsSubnet> implements AwsSubnet {
 		cidr_block: string,
 		map_public_ip_on_launch: boolean,
 		id: string,
-		availability_zone = "us-west-2a",
+		availability_zone: `${awsZone}${char}` = "us-west-2a",
 		autoIam?: boolean,
 		name?: string
 	) {
diff --git a/backend/src/terraform/gce.ts b/backend/src/terraform/gce.ts
index 5202dcf..b2ccf5f 100644
--- a/backend/src/terraform/gce.ts
+++ b/backend/src/terraform/gce.ts
@@ -1,11 +1,11 @@
-import {machineType} from "../types/terraform";
+import {machineType, gcpZone} from "../types/terraform";
 import {jsonRoot} from "./util";
 import {Resource} from "./resource";
 
 export interface Gce {
 	project: string;
 	machine_type: machineType;
-	zone: string;
+	zone: gcpZone;
 	disk_image: string;
 }
 export class Gce extends Resource<Gce> implements Gce {
@@ -20,7 +20,7 @@ export class Gce extends Resource<Gce> implements Gce {
 		id: string,
 		machine_type: machineType,
 		disk_image: string,
-		zone = "us-west1-a"
+		zone: gcpZone = "us-west1-a"
 	) {
 		super(id, "Gce");
 		this.project = project;
diff --git a/backend/src/terraform/googleProvider.ts b/backend/src/terraform/googleProvider.ts
index 8c621aa..d48ef6f 100644
--- a/backend/src/terraform/googleProvider.ts
+++ b/backend/src/terraform/googleProvider.ts
@@ -3,14 +3,16 @@ import {DatabaseModel, generateSchema} from "../types/database";
 import {
 	named,
 	NamedRequiredProvider,
-	RequiredProvider
+	RequiredProvider,
+	gcpZone,
+	gcpRegion
 } from "../types/terraform";
 import {removeName} from "./util";
 
 export interface GoogleProvider extends named<RequiredProvider, "google"> {
 	project: string;
-	region?: string;
-	zone?: string;
+	region?: gcpRegion;
+	zone?: gcpZone;
 	credentials?: string;
 }
 export class GoogleProvider
@@ -20,14 +22,14 @@ export class GoogleProvider
 	name: "google";
 
 	constructor(project: string);
-	constructor(project: string, region: string);
-	constructor(project: string, region: string, zone: string);
+	constructor(project: string, region: gcpRegion);
+	constructor(project: string, region: gcpRegion, zone: gcpZone);
 	constructor(
 		project: string,
 		source = "hashicorp/google",
 		version = ">= 4.10.0",
-		region = "us-west1",
-		zone: string | null = null,
+		region: gcpRegion = "us-west1",
+		zone: gcpZone | null = null,
 		credentials: string | null = null
 	) {
 		super(source, version, "google");
diff --git a/backend/src/types/terraform.ts b/backend/src/types/terraform.ts
index bd615fc..6112a52 100644
--- a/backend/src/types/terraform.ts
+++ b/backend/src/types/terraform.ts
@@ -296,6 +296,39 @@ export interface Firewall {
 	cidr_blocks?: string[];
 }
 
+export type char =
+	| "a"
+	| "b"
+	| "c"
+	| "d"
+	| "e"
+	| "f"
+	| "g"
+	| "h"
+	| "i"
+	| "j"
+	| "k"
+	| "l"
+	| "m"
+	| "n"
+	| "o"
+	| "p"
+	| "q"
+	| "r"
+	| "s"
+	| "t"
+	| "u"
+	| "v"
+	| "w"
+	| "x"
+	| "y"
+	| "z";
+export type digit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9";
+export type countryCode = "us" | "af" | "ap" | "ca" | "eu" | "me" | "sa";
+export type awsZone = `${countryCode}-${string}-${digit}`;
+export type gcpRegion = `${string}-${string}${digit}`;
+export type gcpZone = `${string}-${string}${digit}-${char}`;
+
 // ----------------------------Terraform Root-------------------------------- //
 
 export interface Terraform {