perf: eliminate findUnique roundtrip with optimistic direct insert & eager prisma connect

src/app/api/shorten/route.ts

@@ -2,7 +2,7 @@ import { NextResponse } from "next/server";
 import bcrypt from "bcryptjs";
 import { prisma } from "@/lib/prisma";
 import { getCurrentUser } from "@/lib/auth";
-import { generateUniqueShortCode } from "@/lib/short-code";
+import { generateRandomCode, getDefaultUrlLength } from "@/lib/short-code";
 import { generateQRCodeDataUrl } from "@/lib/qr";
 
 export async function POST(req: Request) {
@@ -41,37 +41,6 @@ export async function POST(req: Request) {
       );
     }
 
-    // Determine short code
-    let shortCode = "";
-    if (custom_code && typeof custom_code === "string") {
-      const trimmedCode = custom_code.trim();
-      if (!/^[a-zA-Z0-9_-]{3,20}$/.test(trimmedCode)) {
-        return NextResponse.json(
-          { success: false, message: "Mã rút gọn chỉ chứa chữ cái, chữ số, dấu gạch dưới hoặc gạch ngang (từ 3-20 ký tự)" },
-          { status: 422 }
-        );
-      }
-
-      // Check collision
-      const existing = await prisma.shortUrl.findUnique({
-        where: { shortCode: trimmedCode },
-      });
-      if (existing) {
-        return NextResponse.json({ success: false, message: "Mã rút gọn này đã được sử dụng. Vui lòng chọn mã khác." }, { status: 409 });
-      }
-      shortCode = trimmedCode;
-    } else {
-      // Auto-generate using configured default_url_length
-      shortCode = await generateUniqueShortCode();
-    }
-    const tCodeGen = performance.now();
-
-    // Hash password if set
-    let hashedPassword: string | null = null;
-    if (password && typeof password === "string" && password.trim().length >= 4) {
-      hashedPassword = await bcrypt.hash(password.trim(), 10);
-    }
-
     // Process Tags
     let tagConnectList: { name: string }[] = [];
     if (tags && typeof tags === "string") {
@@ -93,32 +62,84 @@ export async function POST(req: Request) {
       }
     }
 
-    // Create ShortUrl in DB immediately (instant response)
-    const createdUrl = await prisma.shortUrl.create({
-      data: {
-        originalUrl: url.trim(),
-        shortCode,
-        title: null,
-        password: hashedPassword,
-        expiresAt: expirationDate,
-        displayOnPortal: Boolean(display_on_portal),
-        userId: user ? user.id : null,
-        tags: {
-          connectOrCreate: tagConnectList.map((tag) => ({
-            where: { name: tag.name },
-            create: { name: tag.name },
-          })),
-        },
-      },
-      include: {
-        tags: true,
-      },
-    });
-    const tDbCreate = performance.now();
+    // Hash password if set
+    let hashedPassword: string | null = null;
+    if (password && typeof password === "string" && password.trim().length >= 4) {
+      hashedPassword = await bcrypt.hash(password.trim(), 10);
+    }
+
+    let customShortCode = "";
+    if (custom_code && typeof custom_code === "string") {
+      const trimmedCode = custom_code.trim();
+      if (!/^[a-zA-Z0-9_-]{3,20}$/.test(trimmedCode)) {
+        return NextResponse.json(
+          { success: false, message: "Mã rút gọn chỉ chứa chữ cái, chữ số, dấu gạch dưới hoặc gạch ngang (từ 3-20 ký tự)" },
+          { status: 422 }
+        );
+      }
+      customShortCode = trimmedCode;
+    }
+
+    // Prepare insert data
+    const insertData: any = {
+      originalUrl: url.trim(),
+      title: null,
+      password: hashedPassword,
+      expiresAt: expirationDate,
+      displayOnPortal: Boolean(display_on_portal),
+      userId: user ? user.id : null,
+    };
+
+    if (tagConnectList.length > 0) {
+      insertData.tags = {
+        connectOrCreate: tagConnectList.map((tag) => ({
+          where: { name: tag.name },
+          create: { name: tag.name },
+        })),
+      };
+    }
+
+    let finalShortCode = customShortCode;
+    let createdUrl: any = null;
+
+    if (customShortCode) {
+      const existing = await prisma.shortUrl.findUnique({
+        where: { shortCode: customShortCode },
+        select: { id: true },
+      });
+      if (existing) {
+        return NextResponse.json({ success: false, message: "Mã rút gọn này đã được sử dụng. Vui lòng chọn mã khác." }, { status: 409 });
+      }
+
+      createdUrl = await prisma.shortUrl.create({
+        data: { ...insertData, shortCode: customShortCode },
+        include: tagConnectList.length > 0 ? { tags: true } : undefined,
+      });
+    } else {
+      // Optimistic single-roundtrip direct insert (No pre-checking query needed)
+      const length = await getDefaultUrlLength();
+      for (let attempt = 0; attempt < 3; attempt++) {
+        const candidateCode = generateRandomCode(length + (attempt > 0 ? 1 : 0));
+        try {
+          createdUrl = await prisma.shortUrl.create({
+            data: { ...insertData, shortCode: candidateCode },
+            include: tagConnectList.length > 0 ? { tags: true } : undefined,
+          });
+          finalShortCode = candidateCode;
+          break;
+        } catch (err: any) {
+          if (err.code === "P2002" && attempt < 2) {
+            continue; // Collision retry
+          }
+          throw err;
+        }
+      }
+    }
+    const tDb = performance.now();
 
     // Build absolute short URL
     const appUrl = (process.env.NEXT_PUBLIC_APP_URL || "http://localhost:3000").replace(/\/$/, "");
-    const fullShortUrl = `${appUrl}/${shortCode}`;
+    const fullShortUrl = `${appUrl}/${finalShortCode}`;
 
     // Generate QR Code
     const qrCodeDataUrl = await generateQRCodeDataUrl(fullShortUrl, { size: 240 });
@@ -128,7 +149,7 @@ export async function POST(req: Request) {
       success: true,
       data: {
         id: createdUrl.id,
-        short_code: shortCode,
+        short_code: finalShortCode,
         short_url: fullShortUrl,
         original_url: createdUrl.originalUrl,
         title: createdUrl.title,
@@ -136,13 +157,12 @@ export async function POST(req: Request) {
         expires_at: createdUrl.expiresAt,
         is_password_protected: Boolean(createdUrl.password),
         display_on_portal: createdUrl.displayOnPortal,
-        tags: createdUrl.tags.map((t) => t.name),
+        tags: createdUrl.tags ? createdUrl.tags.map((t: any) => t.name) : [],
       },
       _timings: {
         auth_ms: Math.round(tAuth - t0),
-        code_gen_ms: Math.round(tCodeGen - tAuth),
-        db_create_ms: Math.round(tDbCreate - tCodeGen),
-        qr_ms: Math.round(tQr - tDbCreate),
+        db_insert_ms: Math.round(tDb - tAuth),
+        qr_ms: Math.round(tQr - tDb),
         total_server_ms: Math.round(tQr - t0),
       },
     });

src/lib/prisma.ts

@@ -11,3 +11,6 @@ export const prisma =
   });
 
 globalForPrisma.prisma = prisma;
+
+// Eagerly initiate database connection in background to avoid cold handshake latency
+prisma.$connect().catch(() => {});