Lambda Enrich Data

An AWS Lambda function that enriches incoming request data with user preferences stored in DynamoDB.

Overview

This Lambda function intercepts requests and enriches the payload with user-specific preferences (language, notification settings, etc.) fetched from a DynamoDB table. If no user preferences are found, sensible defaults are applied.

Features

• Data Enrichment: Automatically merges user preferences into request payloads
• Default Fallback: Applies default preferences when user data is not found
• Error Handling: Comprehensive error handling with proper HTTP status codes
• Logging: Structured logging for debugging and monitoring
• Flexible Input: Supports both direct Lambda invocation and API Gateway events

Environment Variables

Variable	Description	Required
TABLE_NAME	Name of the DynamoDB table containing user preferences	Yes

DynamoDB Table Schema

The function expects a DynamoDB table with the following structure:

Attribute	Type	Description
id	String (Partition Key)	Unique user identifier
language	String	User's preferred language code
notifications_enabled	Boolean	Whether notifications are enabled

Request Format

{
  "body": "{\"id\": \"user123\", \"data\": \"example\"}"
}

Response Format

Success (200)

{
  "statusCode": 200,
  "body": "{\"id\": \"user123\", \"data\": \"example\", \"language\": \"en\", \"notifications_enabled\": false}",
  "headers": {
    "Content-Type": "application/json"
  }
}

Error (400/500)

{
  "statusCode": 400,
  "body": "{\"error\": \"Invalid JSON in request body\"}",
  "headers": {
    "Content-Type": "application/json"
  }
}

Default Preferences

When user preferences are not found in DynamoDB:

Preference	Default Value
language	"en"
notifications_enabled	false

Deployment

1. Create DynamoDB Table:

   aws dynamodb create-table \
     --table-name UserPreferences \
     --attribute-definitions AttributeName=id,AttributeType=S \
     --key-schema AttributeName=id,KeyType=HASH \
     --billing-mode PAY_PER_REQUEST

2. Deploy Lambda Function:

   zip function.zip lambda_function.py
   aws lambda create-function \
     --function-name enrich-data \
     --runtime python3.12 \
     --handler lambda_function.lambda_handler \
     --zip-file fileb://function.zip \
     --role arn:aws:iam::ACCOUNT_ID:role/lambda-role \
     --environment Variables={TABLE_NAME=UserPreferences}

3. Set IAM Permissions: Ensure the Lambda execution role has dynamodb:GetItem permission on the table.

Local Development

# Install dependencies
pip install boto3

# Set environment variables
export TABLE_NAME=UserPreferences

# Run locally with AWS credentials configured
python -c "from lambda_function import lambda_handler; print(lambda_handler({'body': '{\"id\": \"test\"}'}, None))"