Prisma Read Replica Middleware

We have provided this middleware as an example only, and without warranty. It is not intended for use in a production environment. Please consider the limitations documented below before adding it to your application.

Find implementation examples here.

Installation

1. npm i @prisma/prisma-read-replica-middleware --save

Usage

1. Create a new file adjacent to your schema.prisma called read-replica-schema.prisma.
2. Inside read-replica-schema.prisma add only generator and datasource blocks.
3. In the generator block, set output to read-replica-client.
4. In the datasource block, add the URL of your read replica database.
5. As part of your build process locally and in all environments, run prisma-read-replica generate to generate the Read Replica client.
6. Wherever you instantiate Prisma using new PrismaClient(), instantiate PrismaReadReplica and apply it with $use. For example:

import { Prisma, PrismaClient } from '@prisma/client'
import PrismaReadReplicaMiddleware from 'prisma-read-replica-middleware';

const modelsToExclude = ['User'];

prisma.$use(PrismaReadReplicaMiddleware(modelsToExclude));

Limitations

1. This middleware does not perform migrations against a read replica database.
2. This middleware only intercepts the following actions: find, findMany, findUnique
3. This middleware does not account for custom providers.
4. This middleware does not account for nested reads because middleware does not have access to the underlying SQL query. In the following example the request will not be sent to the Read Replica because User is an excluded model.

import { Prisma, PrismaClient } from '@prisma/client'
import PrismaReadReplicaMiddleware from 'prisma-read-replica';

const prisma = new PrismaClient({
  log: ['query', 'info', 'warn', 'error'],
});

const modelsToExclude = ['User'];

prisma.$use(PrismaReadReplicaMiddleware(modelsToExclude));

const getUsers = await prisma.user.findMany({
  where: {
    email: {
      contains: 'test',
    },
  },
  include: {
    post: true,
  },
})