Skip to main content



Bemi plugs into Prisma and PostgreSQL to track database changes automatically. It unlocks robust context-aware audit trails and time travel querying inside your application.

This package is a recommended Prisma integration, enabling you to pass application-specific context when performing database changes. This can include context such as the 'where' (API endpoint, worker, etc.), 'who' (user, cron job, etc.), and 'how' behind a change, thereby enriching the information captured by Bemi.

See this example repo as an Todo app example with Prisma that automatically tracks and contextualizes all changes.


  • PostgreSQL 14+
  • Prisma


  1. Install the NPM package
npm install @bemi-db/prisma
  1. Generate a Prisma migration file to add lightweight PostgreSQL triggers for passing application context with all data changes into PostgreSQL replication log
npx bemi migration:create
  1. Run the Prisma migration
npx prisma migrate dev


Enable the new Prisma driver adapters to use a native PostgreSQL client for Node.js by adding the following:

generator client {
previewFeatures = ["driverAdapters"]

Enable PostgreSQL adapter for your Prisma client by using withPgAdapter:

import { withPgAdapter } from "@bemi-db/prisma";
import { PrismaClient } from '@prisma/client';

const prisma = withPgAdapter(new PrismaClient());

Now you can specify custom application context that will be automatically passed with all data changes by following the code examples below.

Application context:

  • Is bound to the current asynchronous runtime execution context, for example, an HTTP request.
  • Is used only with INSERT, UPDATE, DELETE SQL queries performed via Prisma. Otherwise, it is a no-op.
  • Is passed directly into PG Write-Ahead Log with data changes without affecting the structure of the database and SQL queries.

Application context will automatically include the original SQL query that performed data changes, which is generally useful for troubleshooting purposes.


Add the setContext Express.js middleware to pass application context with all underlying data changes made within an HTTP request:

import { setContext } from "@bemi-db/prisma";
import express, { Request } from "express";

const app = express();

// Customizable context
setContext((req: Request) => ({
userId: req.user?.id,
endpoint: req.url,
params: req.body,

Apollo Server

If you use Apollo Server, it's possible use the BemiApolloServerPlugin to pass application context with all underlying data changes made within a GraphQL request:

import { BemiApolloServerPlugin } from "@bemi-db/prisma";
import { ApolloServer } from "@apollo/server";

new ApolloServer({
plugins: [
// Customizable context
BemiApolloServerPlugin(({ request, contextValue }: any) => ({
userId: contextValue.userId,
operationName: request.operationName,
variables: request.variables,
endpoint: request.http.headers.get('origin'),


With Next.js API Routes, it is possible to use the bemiContext function to set application context in a handler function:

import { bemiContext } from "@bemi-db/prisma";
import type { NextApiRequest, NextApiResponse } from "next";

export default function handler(req: NextApiRequest, res: NextApiResponse) {
// Customizable context
bemiContext({ url: req.url, userToken: req.cookies['user-token'] });

// ...

Alternatively, you can use our Express.js-compatible setContext middleware with next-connect:

import { setContext } from "@bemi-db/prisma";
import { createRouter, expressWrapper } from "next-connect";
import type { NextApiRequest, NextApiResponse } from "next";

const router = createRouter<NextApiRequest, NextApiResponse>();

// Customizable context
setContext((req) => ({ url: req.url, userToken: req.cookies['user-token'] }))
).get((req, res) => {
// ...

export default router.handler({
onError: (err, req, res) => { res.status(500).end(err.message) },

Note that Next.js middlewares are not supported because they cannot be executed with the Node.js Runtime, see this discussion.

Inline context

It is also possible to manually set or override context by using the bemiContext function:

import { bemiContext } from "@bemi-db/prisma";

const MyWorker = () => {
bemiContext({ worker: 'MyWorker', stage: 'calculate' })
// ...

bemiContext({ worker: 'MyWorker', stage: 'store' })
// ...


If your database uses a self-signed SSL certificate and you want to enforce using it, you can modify your Connection URL to include the following arguments:


The sslrootcert argument can be a relative or an absolute path pointing to your self-signed SSL certificate.

Database connection

Connect your PostgreSQL source database on to start ingesting and storing all data changes stitched together with application-specific context. The database connection details can be securely configured through the dashboard UI in a few seconds.


Once your destination PostgreSQL database has been fully provisioned, you'll see a "Connected" status. You can now test the connection after making database changes in your connected source database:

psql postgres://[USERNAME]:[PASSWORD]@[HOSTNAME]:5432/[DATABASE] -c 'SELECT "primary_key", "table", "operation", "before", "after", "context", "committed_at" FROM changes;'

primary_key | table | operation | before | after | context | committed_at
26 | todo | CREATE | {} | {"id": 26, "task": "Sleep", "isCompleted": false} | {"userId": 187234, "endpoint": "/todo", "params": {"task": "Sleep", "isCompleted": false}, "SQL": "INSERT INTO ..."} | 2023-12-11 17:09:09+00
27 | todo | CREATE | {} | {"id": 27, "task": "Eat", "isCompleted": false} | {"userId": 187234, "endpoint": "/todo", "params": {"task": "Eat", "isCompleted": false}, "SQL": "INSERT INTO ..."} | 2023-12-11 17:09:11+00
28 | todo | CREATE | {} | {"id": 28, "task": "Repeat", "isCompleted": false} | {"userId": 187234, "endpoint": "/todo", "params": {"task": "Repeat", "isCompleted": false}, "SQL": "INSERT INTO ..."} | 2023-12-11 17:09:13+00
26 | todo | UPDATE | {"id": 26, "task": "Sleep", "isCompleted": false} | {"id": 26, "task": "Sleep", "isCompleted": true} | {"userId": 187234, "endpoint": "/todo/complete", "params": {"id": 26}, "SQL": "UPDATE ..."} | 2023-12-11 17:09:15+00
27 | todo | DELETE | {"id": 27, "task": "Eat", "isCompleted": false} | {} | {"userId": 187234, "endpoint": "/todo/27", "params": {"id": 27}, "SQL": "DELETE FROM ..."} | 2023-12-11 17:09:18+00

See Destination Database for more details.

Data change querying

Lastly, connect to the Bemi PostgreSQL destination database to easily query change data from your application.

To query the read-only historical data, add a new Prisma schema

datasource db {
provider = "postgresql"

generator client {
provider = "prisma-client-js"
output = "./generated/bemi"

model Change {
id String @id
primaryKey String @map("primary_key")
before Json
after Json
context Json
database String
schema String
table String
operation String
committedAt DateTime @map("committed_at")
createdAt DateTime @map("created_at")


Generate Prisma client:

npx prisma generate --schema prisma/bemi.prisma

Initialize a new Prisma client connected to the destination database:

import { PrismaClient } from '../prisma/generated/bemi'

const bemiPrisma = new PrismaClient()

Query changes from the destination database:

const changes = await bemiPrisma.change.findMany({
where: { table: "todo", context: { path: ['userId'], equals: 1 } },
orderBy: { committedAt: "desc" },
take: 1,

Or by using a raw SQL query:

const changes = await bemiPrisma.$queryRaw`
SELECT * FROM "changes"
WHERE "table" = 'todo' AND "context" @> '{"userId": 1}'
ORDER BY "committed_at" DESC


Distributed under the terms of the LGPL-3.0. If you need to modify and distribute the code, please release it to contribute back to the open-source community.