Stream vs polling comparison in DynamoDB - Hands-On Comparison

Stream vs Polling Comparison in DynamoDB

📖 Scenario: You are building a simple inventory tracking system using DynamoDB. You want to understand how to detect changes in your inventory data efficiently.Two common methods are DynamoDB Streams and polling the table for changes. This project will help you set up both methods step-by-step to compare how they work.

🎯 Goal: Build a DynamoDB table with sample inventory data, configure a stream on the table, and write a polling query to fetch recent changes. This will help you see the difference between using streams and polling for data updates.

📋 What You'll Learn

Create a DynamoDB table named Inventory with a primary key ItemID.

Insert sample items with exact ItemID and Quantity values.

Enable DynamoDB Streams on the Inventory table with NEW_IMAGE view type.

Write a polling query to scan the Inventory table for items with Quantity less than 10.

💡 Why This Matters

🌍 Real World

Many applications need to react to data changes in real time. DynamoDB Streams provide an efficient way to capture these changes without repeatedly scanning the table.

💼 Career

Understanding streams and polling is important for backend developers and cloud engineers working with AWS DynamoDB to build scalable and responsive applications.

1

Create DynamoDB Table and Insert Sample Data

Create a DynamoDB table called Inventory with ItemID as the primary key (string). Insert these exact items into the table: {"ItemID": "A101", "Quantity": 15}, {"ItemID": "B202", "Quantity": 8}, and {"ItemID": "C303", "Quantity": 20}.

DynamoDB

# Create the Inventory table and insert the sample items
# Your code here

Need a hint?

Use AWS CLI commands create-table and put-item with exact attribute names and values.

2

Enable DynamoDB Streams on the Inventory Table

Enable DynamoDB Streams on the Inventory table with the stream view type set to NEW_IMAGE.

DynamoDB

aws dynamodb create-table --table-name Inventory --attribute-definitions AttributeName=ItemID,AttributeType=S --key-schema AttributeName=ItemID,KeyType=HASH --provisioned-throughput ReadCapacityUnits=5,WriteCapacityUnits=5

aws dynamodb put-item --table-name Inventory --item '{"ItemID": {"S": "A101"}, "Quantity": {"N": "15"}}'
aws dynamodb put-item --table-name Inventory --item '{"ItemID": {"S": "B202"}, "Quantity": {"N": "8"}}'
aws dynamodb put-item --table-name Inventory --item '{"ItemID": {"S": "C303"}, "Quantity": {"N": "20"}}'

# Enable DynamoDB Streams with NEW_IMAGE view type
# Your code here

Need a hint?

Use the update-table command with --stream-specification to enable streams.

3

Write a Polling Query to Find Low Stock Items

Write a DynamoDB scan command to find items in the Inventory table where Quantity is less than 10.

DynamoDB

aws dynamodb create-table --table-name Inventory --attribute-definitions AttributeName=ItemID,AttributeType=S --key-schema AttributeName=ItemID,KeyType=HASH --provisioned-throughput ReadCapacityUnits=5,WriteCapacityUnits=5

aws dynamodb put-item --table-name Inventory --item '{"ItemID": {"S": "A101"}, "Quantity": {"N": "15"}}'
aws dynamodb put-item --table-name Inventory --item '{"ItemID": {"S": "B202"}, "Quantity": {"N": "8"}}'
aws dynamodb put-item --table-name Inventory --item '{"ItemID": {"S": "C303"}, "Quantity": {"N": "20"}}'

aws dynamodb update-table --table-name Inventory --stream-specification StreamEnabled=true,StreamViewType=NEW_IMAGE

# Write a scan command to find items with Quantity less than 10
# Your code here

Need a hint?

Use the scan command with a filter expression to find items with Quantity less than 10.

4

Complete Setup by Describing the Stream ARN

Add a command to describe the Inventory table and show the Stream ARN to confirm the stream is enabled.

DynamoDB

aws dynamodb create-table --table-name Inventory --attribute-definitions AttributeName=ItemID,AttributeType=S --key-schema AttributeName=ItemID,KeyType=HASH --provisioned-throughput ReadCapacityUnits=5,WriteCapacityUnits=5

aws dynamodb put-item --table-name Inventory --item '{"ItemID": {"S": "A101"}, "Quantity": {"N": "15"}}'
aws dynamodb put-item --table-name Inventory --item '{"ItemID": {"S": "B202"}, "Quantity": {"N": "8"}}'
aws dynamodb put-item --table-name Inventory --item '{"ItemID": {"S": "C303"}, "Quantity": {"N": "20"}}'

aws dynamodb update-table --table-name Inventory --stream-specification StreamEnabled=true,StreamViewType=NEW_IMAGE

aws dynamodb scan --table-name Inventory --filter-expression "Quantity < :val" --expression-attribute-values '{":val":{"N":"10"}}'

# Describe the Inventory table to show the Stream ARN
# Your code here

Need a hint?

Use the describe-table command with a query to show the Stream ARN.