diff --git a/app/api/vip/check-by-user/route.ts b/app/api/vip/check-by-user/route.ts
index 4ab51e1..cd4b359 100644
--- a/app/api/vip/check-by-user/route.ts
+++ b/app/api/vip/check-by-user/route.ts
@@ -16,6 +16,30 @@ type PayjsVipResult = {
 };
 
 const inflightUserChecks = new Map<string, Promise<PayjsVipResult | null>>();
+const inflightUserRequests = new Map<
+  string,
+  Promise<{
+    ok: true;
+    vip: boolean;
+    alreadyLinked: boolean;
+    email?: string;
+    linkedUserId?: string;
+  }>
+>();
+const userCheckResultCache = new Map<
+  string,
+  {
+    expiresAt: number;
+    payload: {
+      ok: true;
+      vip: boolean;
+      alreadyLinked: boolean;
+      email?: string;
+      linkedUserId?: string;
+    };
+  }
+>();
+const USER_CHECK_CACHE_TTL_MS = Number(process.env.CHECK_BY_USER_CACHE_TTL_MS) || 10_000;
 
 async function fetchPayjsVipWithRetry(
   url: string,
@@ -126,139 +150,167 @@ export async function POST(request: NextRequest) {
     );
   }
 
-  let payjsResult: PayjsVipResult | null = null;
-  let vip = false;
-  let email: string | null = null;
-  let linkedUserId: string | undefined;
-  let vipFromSite = false;
-  let vipFromPayments = false;
-  let vipSource = vip ? "payjsapi" : "none";
+  const cached = userCheckResultCache.get(userId);
+  if (cached && cached.expiresAt > Date.now()) {
+    return NextResponse.json(cached.payload);
+  }
+  if (cached) {
+    userCheckResultCache.delete(userId);
+  }
 
-  try {
-    const adminToken = await getAdminToken().catch((error) => {
-      console.error("[check-by-user] getAdminToken failed:", error);
-      return null;
-    });
-    if (!adminToken) {
-      payjsResult = await checkVipFromPayjsapi(request, userId);
-      vip = !!payjsResult?.vip;
-      email = payjsResult?.email ?? null;
-      console.error("[check-by-user] missing PocketBase admin token, fallback to payjs result");
-      return NextResponse.json({
+  const inflight = inflightUserRequests.get(userId);
+  if (inflight) {
+    const payload = await inflight;
+    return NextResponse.json(payload);
+  }
+
+  const task = (async () => {
+    let payjsResult: PayjsVipResult | null = null;
+    let vip = false;
+    let email: string | null = null;
+    let linkedUserId: string | undefined;
+    let vipFromSite = false;
+    let vipFromPayments = false;
+    let vipSource = vip ? "payjsapi" : "none";
+
+    try {
+      const adminToken = await getAdminToken().catch((error) => {
+        console.error("[check-by-user] getAdminToken failed:", error);
+        return null;
+      });
+      if (!adminToken) {
+        payjsResult = await checkVipFromPayjsapi(request, userId);
+        vip = !!payjsResult?.vip;
+        email = payjsResult?.email ?? null;
+        console.error("[check-by-user] missing PocketBase admin token, fallback to payjs result");
+        return {
+          ok: true,
+          vip,
+          alreadyLinked: !!email,
+          email: email ?? undefined,
+        };
+      }
+
+      if (!vip) {
+        vipFromSite = await checkSiteVipByUserId(adminToken, userId);
+        vip = vipFromSite;
+        if (!vip) {
+          vipFromPayments = await checkPaymentsByUserId(adminToken, userId);
+          vip = vipFromPayments;
+        }
+        if (vipFromSite) {
+          vipSource = "pocketbase:site_vip";
+        } else if (vipFromPayments) {
+          vipSource = "pocketbase:payments";
+        }
+        console.log(
+          "[check-by-user] pb fallback user_id=%s site_vip=%s payments=%s",
+          userId,
+          vipFromSite,
+          vipFromPayments
+        );
+      }
+
+      // PB 未命中再请求 payjsapi，避免每次都先走远端网络
+      if (!vip) {
+        payjsResult = await checkVipFromPayjsapi(request, userId);
+        if (payjsResult?.vip) {
+          vip = true;
+          email = payjsResult.email ?? null;
+          vipSource = "payjsapi";
+        }
+      }
+
+      if (isAnonymousUserId(userId)) {
+        const linkRecord = await findVipEmailLinkByAnonymousUserId(adminToken, userId);
+        const linkEmail =
+          typeof linkRecord?.email === "string"
+            ? linkRecord.email.trim().toLowerCase()
+            : "";
+        const linkUserId =
+          typeof linkRecord?.user_id === "string" ? linkRecord.user_id.trim() : "";
+
+        // 匿名 user_id 本身可能已迁移到真实用户，需补查映射用户的 VIP
+        if (!vip && linkUserId && linkUserId !== userId) {
+          const linkedVip = await checkSiteVipByUserId(adminToken, linkUserId);
+          const linkedPaymentVip = linkedVip
+            ? true
+            : await checkPaymentsByUserId(adminToken, linkUserId);
+          if (linkedVip || linkedPaymentVip) {
+            vip = true;
+            linkedUserId = linkUserId;
+            vipSource = linkedVip ? "vip_email_link:site_vip" : "vip_email_link:payments";
+          }
+        }
+
+        if (vip && linkEmail) {
+          email = linkEmail;
+          if (linkUserId && !isAnonymousUserId(linkUserId)) {
+            linkedUserId = linkUserId;
+          }
+          if (!vipSource || vipSource === "none") {
+            vipSource = "vip_email_link";
+          }
+          console.log(
+            "[check-by-user] linked by vip_email_link user_id=%s linkedUserId=%s email=%s",
+            userId,
+            linkedUserId || "(none)",
+            email
+          );
+        } else if (vip) {
+          const linkedMember = await findLinkedMemberFromOrder(adminToken, userId);
+          if (linkedMember) {
+            email = linkedMember.email;
+            linkedUserId = linkedMember.userId;
+            await upsertVipEmailLink(
+              adminToken,
+              linkedMember.email,
+              linkedMember.userId,
+              userId
+            );
+            vipSource = "linked_from_order";
+            console.log(
+              "[check-by-user] linked by order user_id=%s linkedUserId=%s email=%s",
+              userId,
+              linkedUserId,
+              email
+            );
+          }
+        }
+      }
+
+      console.log(
+        "[check-by-user] result user_id=%s vip=%s source=%s alreadyLinked=%s linkedUserId=%s",
+        userId,
+        vip,
+        vipSource,
+        !!email,
+        linkedUserId || "(none)"
+      );
+
+      return {
         ok: true,
         vip,
         alreadyLinked: !!email,
         email: email ?? undefined,
-      });
+        linkedUserId,
+      };
+    } catch (error) {
+      console.error("[check-by-user] failed:", error);
+      // 接口容错：即使 PB 回退失败，也不抛 500 给前端
+      return { ok: true, vip: false, alreadyLinked: false };
     }
+  })();
 
-    if (!vip) {
-      vipFromSite = await checkSiteVipByUserId(adminToken, userId);
-      vip = vipFromSite;
-      if (!vip) {
-        vipFromPayments = await checkPaymentsByUserId(adminToken, userId);
-        vip = vipFromPayments;
-      }
-      if (vipFromSite) {
-        vipSource = "pocketbase:site_vip";
-      } else if (vipFromPayments) {
-        vipSource = "pocketbase:payments";
-      }
-      console.log(
-        "[check-by-user] pb fallback user_id=%s site_vip=%s payments=%s",
-        userId,
-        vipFromSite,
-        vipFromPayments
-      );
-    }
-
-    // PB 未命中再请求 payjsapi，避免每次都先走远端网络
-    if (!vip) {
-      payjsResult = await checkVipFromPayjsapi(request, userId);
-      if (payjsResult?.vip) {
-        vip = true;
-        email = payjsResult.email ?? null;
-        vipSource = "payjsapi";
-      }
-    }
-
-    if (isAnonymousUserId(userId)) {
-      const linkRecord = await findVipEmailLinkByAnonymousUserId(adminToken, userId);
-      const linkEmail =
-        typeof linkRecord?.email === "string"
-          ? linkRecord.email.trim().toLowerCase()
-          : "";
-      const linkUserId =
-        typeof linkRecord?.user_id === "string" ? linkRecord.user_id.trim() : "";
-
-      // 匿名 user_id 本身可能已迁移到真实用户，需补查映射用户的 VIP
-      if (!vip && linkUserId && linkUserId !== userId) {
-        const linkedVip = await checkSiteVipByUserId(adminToken, linkUserId);
-        const linkedPaymentVip = linkedVip
-          ? true
-          : await checkPaymentsByUserId(adminToken, linkUserId);
-        if (linkedVip || linkedPaymentVip) {
-          vip = true;
-          linkedUserId = linkUserId;
-          vipSource = linkedVip ? "vip_email_link:site_vip" : "vip_email_link:payments";
-        }
-      }
-
-      if (vip && linkEmail) {
-        email = linkEmail;
-        if (linkUserId && !isAnonymousUserId(linkUserId)) {
-          linkedUserId = linkUserId;
-        }
-        if (!vipSource || vipSource === "none") {
-          vipSource = "vip_email_link";
-        }
-        console.log(
-          "[check-by-user] linked by vip_email_link user_id=%s linkedUserId=%s email=%s",
-          userId,
-          linkedUserId || "(none)",
-          email
-        );
-      } else if (vip) {
-        const linkedMember = await findLinkedMemberFromOrder(adminToken, userId);
-        if (linkedMember) {
-          email = linkedMember.email;
-          linkedUserId = linkedMember.userId;
-          await upsertVipEmailLink(
-            adminToken,
-            linkedMember.email,
-            linkedMember.userId,
-            userId
-          );
-          vipSource = "linked_from_order";
-          console.log(
-            "[check-by-user] linked by order user_id=%s linkedUserId=%s email=%s",
-            userId,
-            linkedUserId,
-            email
-          );
-        }
-      }
-    }
-
-    console.log(
-      "[check-by-user] result user_id=%s vip=%s source=%s alreadyLinked=%s linkedUserId=%s",
-      userId,
-      vip,
-      vipSource,
-      !!email,
-      linkedUserId || "(none)"
-    );
-
-    return NextResponse.json({
-      ok: true,
-      vip,
-      alreadyLinked: !!email,
-      email: email ?? undefined,
-      linkedUserId,
+  inflightUserRequests.set(userId, task);
+  try {
+    const payload = await task;
+    userCheckResultCache.set(userId, {
+      payload,
+      expiresAt: Date.now() + USER_CHECK_CACHE_TTL_MS,
     });
-  } catch (error) {
-    console.error("[check-by-user] failed:", error);
-    // 接口容错：即使 PB 回退失败，也不抛 500 给前端
-    return NextResponse.json({ ok: true, vip: false, error: "check_failed_degraded" });
+    return NextResponse.json(payload);
+  } finally {
+    inflightUserRequests.delete(userId);
   }
 }