Streams & Event Sourcing in AWS Serverless

Introduction

In the realm of AWS Serverless architecture, DynamoDB Streams and Event Sourcing play crucial roles in building reactive and scalable applications. This lesson delves into these concepts, exploring how they can enhance data processing and application design.

Key Concepts

Step-by-Step Process

The following flowchart outlines the process of setting up DynamoDB Streams for Event Sourcing:

            graph TD;
                A[Start] --> B[DynamoDB Table Setup];
                B --> C[Enable DynamoDB Streams];
                C --> D[Set Up Lambda Function];
                D --> E[Process Stream Events];
                E --> F[Store Events in S3 or Event Store];
                F --> G[Query Events for State Restoration];
                G --> H[End];
        

Implementing DynamoDB Streams

To set up DynamoDB Streams, follow these steps:

1. Navigate to the DynamoDB console.
2. Select your table and go to the Exports and streams tab.
3. Enable the stream by selecting New and old images.
4. Configure an AWS Lambda function to trigger on stream events.

Example Lambda Function

Here’s an example of a Lambda function that processes DynamoDB stream records:

        const AWS = require('aws-sdk');
        exports.handler = async (event) => {
            for (const record of event.Records) {
                console.log('DynamoDB Record: ', JSON.stringify(record, null, 2));
                // Process the record here (e.g., save to Event Store)
            }
        };
        

Best Practices

• Use batching for processing stream records to optimize Lambda invocations.
• Implement idempotency in your event processing to handle duplicate events safely.
• Monitor and log stream processing to identify and address potential failures.
• Use versioning for your event schema to handle changes gracefully.

FAQ