@ttoss/lambda-postgres-query

Create an AWS Lambda function to securely query a PostgreSQL database in a private VPC subnet without exposing the database to the internet.

When to Use

This package solves the challenge of querying a PostgreSQL database from AWS Lambda functions without internet access. Traditional approaches require expensive NAT Gateways or complex multi-Lambda architectures. This package provides a simpler solution by deploying a dedicated Lambda function within your VPC.

Installation

pnpm install @ttoss/lambda-postgres-query

Setup

CloudFormation Template

Create a CloudFormation template to deploy the Lambda function:

import { createLambdaPostgresQueryTemplate } from '@ttoss/lambda-postgres-query/cloudformation';

const template = createLambdaPostgresQueryTemplate();

export default template;

Lambda Handler

Create a handler file that exports the Lambda function:

export { handler } from '@ttoss/lambda-postgres-query';

Environment Variables

Configure the following environment variables:

DATABASE_NAME=your_database_name
DATABASE_USERNAME=your_username
DATABASE_PASSWORD=your_password
DATABASE_HOST=your_database_host
DATABASE_HOST_READ_ONLY=your_read_only_host  # Optional
DATABASE_PORT=5432
SECURITY_GROUP_IDS=sg-xxxxx,sg-yyyyy
SUBNET_IDS=subnet-xxxxx,subnet-yyyyy

Deployment

Add a deploy script to your package.json:

{
  "scripts": {
    "deploy": "carlin deploy"
  }
}

Deploy using Carlin:

pnpm deploy

Note: Set lambdaFormat: 'cjs' in your Carlin configuration, as the pg package requires CommonJS.

Usage

Querying from External Lambdas

Query the database from Lambda functions outside the VPC:

import { query } from '@ttoss/lambda-postgres-query';
import type { Handler } from 'aws-lambda';

export const handler: Handler = async (event) => {
  const result = await query('SELECT * FROM users');
  return result.rows;
};

Advanced Query Options

import { query } from '@ttoss/lambda-postgres-query';

// Query with parameters
const result = await query({
  text: 'SELECT * FROM users WHERE id = $1',
  values: [userId],
});

// Use read-only connection
const result = await query({
  text: 'SELECT * FROM users',
  readOnly: true, // Defaults to true
});

// Disable automatic camelCase conversion
const result = await query({
  text: 'SELECT * FROM users',
  camelCaseKeys: false, // Defaults to true
});

// Specify custom Lambda function name
const result = await query({
  text: 'SELECT * FROM users',
  lambdaPostgresQueryFunction: 'custom-function-name',
});

API Reference

createLambdaPostgresQueryTemplate(options?)

Creates a CloudFormation template for the PostgreSQL query Lambda function.

Parameters

• handler (string, optional): Lambda handler function name. Default: 'handler.handler'
• memorySize (number, optional): Lambda memory size in MB. Default: 128
• timeout (number, optional): Lambda timeout in seconds. Default: 30

Returns

A CloudFormation template object.

query(params)

Queries the PostgreSQL database by invoking the VPC Lambda function.

Parameters

Accepts either a SQL string or an options object extending QueryConfig with additional properties:

• text (string): SQL query text
• values (array, optional): Query parameter values
• readOnly (boolean, optional): Use read-only database host if available. Default: true
• lambdaPostgresQueryFunction (string, optional): Name of the query Lambda function. Default: LAMBDA_POSTGRES_QUERY_FUNCTION environment variable
• camelCaseKeys (boolean, optional): Convert snake_case column names to camelCase. Default: true

Returns

A QueryResult object with transformed rows.

handler

AWS Lambda handler function for processing database queries within the VPC.