diff --git a/src/app/api/production-data/route.ts b/src/app/api/production-data/route.ts
index b0783fd..5b1a35d 100644
--- a/src/app/api/production-data/route.ts
+++ b/src/app/api/production-data/route.ts
@@ -1,5 +1,8 @@
 import { NextRequest, NextResponse } from "next/server";
 import sql from "mssql";
+import { apiLogger, formatError } from "../../../server/logger";
+
+const SLOW_QUERY_MS = 3000;
 
 const dbConfig = {
   server: process.env.DB_SERVER!,
@@ -25,6 +28,7 @@ export async function GET(request: NextRequest) {
   }
 
   let pool: sql.ConnectionPool | undefined;
+  const t0 = Date.now();
   try {
     pool = await sql.connect(dbConfig);
     const result = await pool
@@ -53,10 +57,15 @@ export async function GET(request: NextRequest) {
       return serialized;
     });
 
+    const dur = Date.now() - t0;
+    if (dur > SLOW_QUERY_MS) {
+      apiLogger.warn(`slow query · workshopNo=${workshopNo} · dur=${dur}ms · rows=${data.length}`);
+    }
     return NextResponse.json({ columns, data, total: data.length });
   } catch (err) {
+    const dur = Date.now() - t0;
     const message = err instanceof Error ? err.message : "Unknown error";
-    console.error("DB query error:", message);
+    apiLogger.error(`query failed · workshopNo=${workshopNo} · dur=${dur}ms · ${formatError(err)}`);
     return NextResponse.json({ error: message }, { status: 500 });
   } finally {
     if (pool) {