Instantiating the client

Use a single shared instance of PrismaClient

In long-running applications, we recommend that you:

• ✔ Create one instance of PrismaClient and re-use it across your application
• ✔ Assign PrismaClient to a global variable in dev environments only to prevent hot reloading from creating new instances

Note: You do not need to explicitly $disconnect() in the context of a long-running application, such as a GraphQL server.

Multiple instances of PrismaClient results in multiple instances of the query engine. Each query engine creates a connection pool with a default pool size of num_physical_cpus * 2 + 1. Too many connections may start to slow down your database and eventually lead to the following error:

Error in connector: Error querying the database: db error: FATAL: sorry, too many clients already
    at PrismaClientFetcher.request

To re-use a single instance, create a module that exports a PrismaClient object:

client.ts
1import { PrismaClient } from "@prisma/client"
2
3let prisma = new PrismaClient() 
4
5export default prisma

The object is cached the first time the module is imported. Subsequent requests return the cached object rather than creating a new PrismaClient:

app.ts
1import prisma from './client'
2
3async function main() {
4  const allUsers = await prisma.user.findMany();
5}
6
7main();

client.ts
1import { PrismaClient } from "@prisma/client"
2
3declare global {
4    namespace NodeJS {
5        interface Global {
6            prisma: PrismaClient;
7        }
8    }
9}
10
11let prisma: PrismaClient;
12
13if (process.env.NODE_ENV === "production") {
14  prisma = new PrismaClient()
15} else {
16  if (!global.prisma) {
17    global.prisma = new PrismaClient()
18  }
19
20  prisma = global.prisma
21}
22
23export default prisma

app.ts
1import prisma from './client'
2
3async function main() {
4    const allUsers = await prisma.user.findMany();
5}
6
7main();