Next.js Prisma: “PrismaClient is already running” error in development

[trbgaming100]

Hey everyone 👋
I’m using Prisma with Next.js (App Router), and during local development I keep getting this error:

Error: 
Invalid `prisma.user.findMany()` invocation:
PrismaClient is already running a query.

Sometimes I also see:

PrismaClient is unable to be run because it was already started.

It happens randomly after saving files or hot reloading.
Here’s how I’m initializing Prisma:

import { PrismaClient } from "@prisma/client";
const prisma = new PrismaClient();
export default prisma;

Any idea how to fix this during development?

Guidelines

• I have read and understood this category's guidelines before making this post.

[shandilyaaryan]

This happens because Next.js reloads modules frequently in dev mode, and every reload creates a new PrismaClient instance — which overloads the database connection pool.

✅ Fix:
Use a singleton pattern so Prisma reuses the same client instead of reinitializing it on every reload.

Here’s the recommended setup 👇

// lib/prisma.ts
import { PrismaClient } from "@prisma/client";

const globalForPrisma = global as unknown as { prisma: PrismaClient };

export const prisma =
  globalForPrisma.prisma ||
  new PrismaClient({
    log: ["query"],
  });

if (process.env.NODE_ENV !== "production") globalForPrisma.prisma = prisma;

export default prisma;

Then simply import in your code:

import prisma from "@/lib/prisma";

✅ This ensures:

• Only one Prisma client is ever created
• Prevents “already running” or “too many connections” errors
• Works with hot reloading perfectly

[omrharbi]

This usually happens in Next.js (App Router) because every time the dev server hot-reloads, it creates a new PrismaClient instance. After a few reloads, multiple clients exist and Prisma throws:

• “PrismaClient is already running a query”
• “PrismaClient is unable to be run because it was already started”

✅ Fix: Use a global Prisma client in development

Make sure you only create one PrismaClient instance during next dev:

// lib/prisma.ts
import { PrismaClient } from "@prisma/client";

const globalForPrisma = global as unknown as {
  prisma: PrismaClient | undefined;
};

export const prisma =
  globalForPrisma.prisma ??
  new PrismaClient({
    log: ["query", "error", "warn"],
  });

if (process.env.NODE_ENV !== "production") globalForPrisma.prisma = prisma;

Then import it everywhere:

import { prisma } from "@/lib/prisma";

Why this works

global persists across module reloads in development, so the same PrismaClient instance is reused. In production (no hot-reload), a fresh client is created normally.

Extra tips

• Don’t create Prisma clients inside functions, route handlers, or components.
• Make sure the file is imported only from the server (e.g., route handlers, server actions).

After switching to the global client pattern, the error should disappear.