fix: cap Prisma pool during next build to stop deploy SSG timeouts

Next build workers were each opening up to DATABASE_POOL_SIZE connections and exhausting MySQL (pool active=0), hanging sitemap generation. Cap build pool to 5, fail connect faster, limit SSG concurrency, and make sitemap dynamic.

Co-authored-by: Cursor <[email protected]>

next.config.ts

@@ -44,6 +44,8 @@ const nextConfig: NextConfig = {
 			static: 180,
 		},
 		optimizePackageImports: ["lucide-react"],
+		// Keep build-time DB fan-out low (shared MySQL with emulator).
+		staticGenerationMaxConcurrency: 3,
 	},
 
 	// Add caching headers for static assets

src/app/sitemap.ts

@@ -1,6 +1,10 @@
 import type { MetadataRoute } from "next";
 import { prisma } from "@/lib/prisma";
 
+// Built at request time — avoids competing with SSG workers for scarce DB
+// connections during `next build` (pool timeouts killed deploy on sitemap).
+export const dynamic = "force-dynamic";
+
 export default async function sitemap(): Promise<MetadataRoute.Sitemap> {
 	const appUrl = process.env.APP_URL ?? "http://localhost:3000";
 

src/lib/prisma-pool.test.ts

@@ -0,0 +1,19 @@
+import { describe, expect, it } from "vitest";
+import { resolvePrismaConnectionLimit } from "./prisma-pool";
+
+describe("resolvePrismaConnectionLimit", () => {
+	it("caps the pool during production build phases", () => {
+		expect(resolvePrismaConnectionLimit(40, "phase-production-build")).toBe(5);
+		expect(
+			resolvePrismaConnectionLimit(40, "phase-production-compile"),
+		).toBe(5);
+		expect(resolvePrismaConnectionLimit(3, "phase-production-build")).toBe(3);
+	});
+
+	it("keeps the configured pool outside build", () => {
+		expect(resolvePrismaConnectionLimit(40, undefined)).toBe(40);
+		expect(resolvePrismaConnectionLimit(40, "phase-development-server")).toBe(
+			40,
+		);
+	});
+});

src/lib/prisma-pool.ts

@@ -0,0 +1,16 @@
+/**
+ * Cap pool size during `next build` so N workers × pool don't exhaust MySQL.
+ * Kept free of Prisma/env imports so unit tests can exercise it in isolation.
+ */
+export function resolvePrismaConnectionLimit(
+	poolSize: number,
+	phase = process.env.NEXT_PHASE,
+): number {
+	if (
+		phase === "phase-production-build" ||
+		phase === "phase-production-compile"
+	) {
+		return Math.min(poolSize, 5);
+	}
+	return poolSize;
+}

src/lib/prisma.ts

@@ -1,20 +1,29 @@
 import { PrismaMariaDb } from "@prisma/adapter-mariadb";
 import { env } from "@/env";
 import { PrismaClient } from "@/generated/prisma/client";
+import { resolvePrismaConnectionLimit } from "@/lib/prisma-pool";
 
 const globalForPrisma = globalThis as unknown as { prisma?: PrismaClient };
 
 function createPrismaClient(): PrismaClient {
 	const url = new URL(env.DATABASE_URL);
+	const isBuild =
+		process.env.NEXT_PHASE === "phase-production-build" ||
+		process.env.NEXT_PHASE === "phase-production-compile";
+	const connectionLimit = resolvePrismaConnectionLimit(env.DATABASE_POOL_SIZE);
+	// Fail fast during SSG so Next can retry/fallback instead of hanging 30s+.
+	const connectTimeout = isBuild
+		? Math.min(env.DATABASE_CONNECT_TIMEOUT_MS, 5_000)
+		: env.DATABASE_CONNECT_TIMEOUT_MS;
 	const adapter = new PrismaMariaDb({
 		host: url.hostname,
 		port: Number(url.port) || 3306,
 		user: decodeURIComponent(url.username),
 		password: decodeURIComponent(url.password),
 		database: url.pathname.replace(/^\//, ""),
-		connectionLimit: env.DATABASE_POOL_SIZE,
-		connectTimeout: env.DATABASE_CONNECT_TIMEOUT_MS,
-		acquireTimeout: env.DATABASE_CONNECT_TIMEOUT_MS,
+		connectionLimit,
+		connectTimeout,
+		acquireTimeout: connectTimeout,
 		idleTimeout: env.DATABASE_IDLE_TIMEOUT_MS,
 	});
 	return new PrismaClient({