diff --git a/app/api/vip/check-by-user/route.ts b/app/api/vip/check-by-user/route.ts
index cd4b359..80a1fe5 100644
--- a/app/api/vip/check-by-user/route.ts
+++ b/app/api/vip/check-by-user/route.ts
@@ -16,27 +16,22 @@ type PayjsVipResult = {
 };
 
 const inflightUserChecks = new Map<string, Promise<PayjsVipResult | null>>();
+type UserCheckPayload = {
+  ok: boolean;
+  vip: boolean;
+  alreadyLinked: boolean;
+  email?: string;
+  linkedUserId?: string;
+};
 const inflightUserRequests = new Map<
   string,
-  Promise<{
-    ok: true;
-    vip: boolean;
-    alreadyLinked: boolean;
-    email?: string;
-    linkedUserId?: string;
-  }>
+  Promise<UserCheckPayload>
 >();
 const userCheckResultCache = new Map<
   string,
   {
     expiresAt: number;
-    payload: {
-      ok: true;
-      vip: boolean;
-      alreadyLinked: boolean;
-      email?: string;
-      linkedUserId?: string;
-    };
+    payload: UserCheckPayload;
   }
 >();
 const USER_CHECK_CACHE_TTL_MS = Number(process.env.CHECK_BY_USER_CACHE_TTL_MS) || 10_000;