perf(admin): cache global admin list totals via redisCache

Introduce getCachedAdminCount to cache un-filtered table count(*) queries in Redis for admin lists (starting with UsersPage), avoiding heavy full table scans on every request while keeping exact counts for search/filtered queries.

src/app/admin/users/page.tsx

@@ -1,4 +1,4 @@
-import { and, count, desc, eq, gte, like, or } from "drizzle-orm";
+import { and, desc, eq, gte, like, or } from "drizzle-orm";
 import { Users } from "lucide-react";
 import { getTranslations } from "next-intl/server";
 import { AdminPageShell } from "@/components/admin/admin-page-shell";
@@ -6,6 +6,7 @@ import { fetchAdminList } from "@/lib/admin-list";
 import { db, User } from "@/lib/db";
 import { formatNumber } from "@/lib/format-date";
 import { canAccess, PERMS } from "@/lib/permissions";
+import { getCachedAdminCount } from "@/lib/services/admin-stats";
 import { CreateUserDialog } from "./_components/create-user-dialog";
 import { UsersTable } from "./users-table";
 
@@ -43,7 +44,7 @@ export default async function UsersPage({
 					conditions.push(eq(User.online, rawParams.filter_online));
 				}
 				const where = conditions.length > 0 ? and(...conditions) : undefined;
-				const [rows, totals] = await Promise.all([
+				const [rows, total] = await Promise.all([
 					db
 						.select({
 							id: User.id,
@@ -64,9 +65,9 @@ export default async function UsersPage({
 						.orderBy(desc(User.id))
 						.limit(perPage)
 						.offset((page - 1) * perPage),
-					db.select({ total: count() }).from(User).where(where),
+					getCachedAdminCount(User, "users:total", where),
 				]);
-				return { rows, total: totals[0]?.total ?? 0 };
+				return { rows, total };
 			},
 		},
 		paramsPromise,

src/lib/services/admin-stats.ts

@@ -0,0 +1,26 @@
+import { count, type SQL } from "drizzle-orm";
+import type { MySqlTable } from "drizzle-orm/mysql-core";
+import { db } from "@/lib/db";
+import { redisCache } from "@/lib/redis-cache";
+
+/**
+ * Caches admin list totals when no filters are applied (no 'where' clause),
+ * preventing heavy COUNT(*) table scans on every request for large tables.
+ * Filtered queries bypass cache to ensure exact search result counts.
+ */
+export async function getCachedAdminCount(
+	table: MySqlTable,
+	cacheKey: string,
+	where?: SQL | undefined,
+): Promise<number> {
+	// Only cache the global count (where = undefined)
+	if (where) {
+		const [row] = await db.select({ total: count() }).from(table).where(where);
+		return Number(row?.total ?? 0);
+	}
+
+	return await redisCache(`admin:count:${cacheKey}`, 60, async () => {
+		const [row] = await db.select({ total: count() }).from(table);
+		return Number(row?.total ?? 0);
+	});
+}