diff --git a/.vscode/settings.json b/.vscode/settings.json
new file mode 100644
index 0000000..0c0ea44
--- /dev/null
+++ b/.vscode/settings.json
@@ -0,0 +1,4 @@
+{
+	"deno.enable": true,
+	"deno.unstable": true,
+}
diff --git a/routes/index.tsx b/routes/index.tsx
index f56e433..f64e858 100644
--- a/routes/index.tsx
+++ b/routes/index.tsx
@@ -7,7 +7,7 @@ type HandlerResponse = {
 	url?: string;
 	isUpdated?: boolean;
 	error?: string;
-}
+};
 
 export const handler: Handlers = {
 	async POST(req, ctx) {
@@ -17,18 +17,25 @@ export const handler: Handlers = {
 			case "PUT": {
 				const originalUrl = form.get("original_url") as string;
 				const customUrl = form.get("custom_url") as string;
-				const customised = await customiseShortenedUrl(originalUrl, customUrl);
-				return ctx.render({
-					url: customised,
-					isUpdated: true,
-				});
+				try {
+					const customised = await customiseShortenedUrl(
+						originalUrl,
+						customUrl,
+					);
+					return ctx.render({
+						url: customised,
+						isUpdated: true,
+					});
+				} catch {
+					return ctx.render({ error: "Customised url already exists" });
+				}
 			}
 			default: {
 				const originalUrl = form.get("url") as string;
 				if (!originalUrl) return ctx.render({ error: "URL cannot be empty" });
 				const shortened = await shortenUrl(originalUrl);
 				return ctx.render({
-					url: shortened
+					url: shortened,
 				});
 			}
 		}
@@ -38,11 +45,7 @@ export const handler: Handlers = {
 export default function Home(props: PageProps<HandlerResponse>) {
 	return (
 		<div className="flex flex-col gap-10 items-center justify-center h-full">
-			<img
-				src="/assets/wri-logo.png"
-				alt="WRI Logo"
-				class="w-72"
-			/>
+			<img src="/assets/wri-logo.png" alt="WRI Logo" class="w-72" />
 			<form
 				method="POST"
 				className="flex items-center gap-4 p-4 rounded-lg bg-white shadow-lg border border-slate-200"
diff --git a/services/shortener.ts b/services/shortener.ts
index 8fbfb19..9823e15 100644
--- a/services/shortener.ts
+++ b/services/shortener.ts
@@ -1,7 +1,6 @@
 import { nanoid } from 'nanoid';
 
 const kv = await Deno.openKv();
-const KEY_EXPIRY = 90 * 24 * 60 * 60; // 90 days
 
 export async function shortenUrl(url: string) {
 	const token = nanoid(4);
@@ -10,21 +9,27 @@ export async function shortenUrl(url: string) {
 	await kv
 		.atomic()
 		.check({ key, versionstamp: null })
-		.set(["url", token], url, { expireIn: KEY_EXPIRY })
+		.set(["url", token], url)
 		.commit();
 	return token;
 }
 
 export async function customiseShortenedUrl(original: string, customised: string) {
 	const originalKey = ["url", original];
-	const originalShortened = await kv.get(originalKey);
+	const originalShortened = await kv.get<string>(originalKey);
 	const customisedKey = ["url", customised];
+
+	// check if customised already exists
+	if (await kv.get(customisedKey)) {
+		throw new Error("Customised url already exists");
+	}
+
 	await kv
 		.atomic()
 		.check(originalShortened)
 		.check({ key: customisedKey, versionstamp: null })
 		.delete(originalKey)
-		.set(customisedKey, originalShortened.value as string, { expireIn: KEY_EXPIRY })
+		.set(customisedKey, originalShortened.value as string)
 		.commit();
 	return customised;
 }
@@ -34,4 +39,4 @@ export async function resolveUrl(token: string): Promise<string | null> {
 	const url = await kv.get(key);
 	if (!url) return null;
 	return url.value as string;
-}
\ No newline at end of file
+}