Cross-region replication (Global Tables) in DynamoDB - Mini Project: Build & Apply

Cross-region Replication with DynamoDB Global Tables

📖 Scenario: You work for a company that wants to keep its customer data available and synchronized across two different regions to improve reliability and speed for users worldwide.

🎯 Goal: Create a DynamoDB Global Table that replicates data between two regions automatically.

📋 What You'll Learn

Create a DynamoDB table named Customers with a primary key CustomerID (string).

Add a replica configuration for the us-west-2 region.

Enable cross-region replication to keep data synchronized between us-east-1 and us-west-2.

Verify the table has the correct replica settings.

💡 Why This Matters

🌍 Real World

Global Tables help companies keep data synchronized across multiple geographic regions, improving application availability and reducing latency for users worldwide.

💼 Career

Understanding how to configure and manage DynamoDB Global Tables is important for cloud engineers and database administrators working with AWS to build scalable, resilient applications.

1

Create the base DynamoDB table in us-east-1

Create a DynamoDB table named Customers in the us-east-1 region with a primary key called CustomerID of type string.

DynamoDB

# Your code here to create the Customers table with CustomerID as the primary key in us-east-1

Hint

Use the AWS CLI create-table command with the correct attribute and key schema.

2

Add replica configuration for us-west-2 region

Add a replica configuration to the Customers table for the us-west-2 region to enable cross-region replication.

DynamoDB

aws dynamodb create-table \
    --table-name Customers \
    --attribute-definitions AttributeName=CustomerID,AttributeType=S \
    --key-schema AttributeName=CustomerID,KeyType=HASH \
    --billing-mode PAY_PER_REQUEST \
    --region us-east-1
# Your code here to add replica for us-west-2

Hint

Use the --replica-configurations option to specify the replica region.

3

Enable cross-region replication

Use the AWS CLI to update the Customers table in us-east-1 to add a replica in us-west-2 region, enabling cross-region replication.

DynamoDB

aws dynamodb create-table \
    --table-name Customers \
    --attribute-definitions AttributeName=CustomerID,AttributeType=S \
    --key-schema AttributeName=CustomerID,KeyType=HASH \
    --billing-mode PAY_PER_REQUEST \
    --replica-configurations RegionName=us-west-2 \
    --region us-east-1
# Your code here to update the table and enable replication

Hint

Use the update-table command with --replica-updates to add the replica.

4

Verify the Global Table replica settings

Use the AWS CLI to describe the Customers table in us-east-1 and verify that the replica for us-west-2 is configured.

DynamoDB

aws dynamodb update-table \
    --table-name Customers \
    --region us-east-1 \
    --replica-updates '[{"Create":{"RegionName":"us-west-2"}}]'
# Your code here to describe the table and check replicas

Hint

Use the describe-table command to see the replica configuration details.

Practice

1. What is the main purpose of DynamoDB Global Tables in cross-region replication?

easy

A. To keep data copied and synchronized across multiple AWS regions

B. To create backups of tables in the same region

C. To increase the size limit of a single DynamoDB table

D. To encrypt data only in one region

Solution

1. Step 1: Understand Global Tables concept

   Global Tables replicate data automatically across multiple AWS regions to keep them in sync.

2. Step 2: Identify the main purpose

   This replication helps applications stay fast and available worldwide by having data close to users.

3. Final Answer:

   To keep data copied and synchronized across multiple AWS regions -> Option A

4. Quick Check:

   Global Tables = cross-region data sync [OK]

Hint: Global Tables = data sync across regions [OK]

Common Mistakes:

• Confusing backups with replication
• Thinking Global Tables increase table size
• Assuming encryption is the main feature

2. Which AWS CLI command is used to create a DynamoDB Global Table?

easy

A. aws dynamodb delete-global-table --table-name MyTable

B. aws dynamodb create-table --table-name MyTable --region us-east-1

C. aws dynamodb create-global-table --global-table-name MyTable --replication-group RegionName=us-east-1

D. aws dynamodb update-global-table --table-name MyTable

Solution

1. Step 1: Identify the correct command for creating Global Tables

   The command to create a Global Table is create-global-table with replication group specifying regions.

2. Step 2: Check options

   aws dynamodb create-global-table --global-table-name MyTable --replication-group RegionName=us-east-1 uses create-global-table with replication group, which is correct. Others are for creating normal tables, updating, or deleting.

3. Final Answer:

   aws dynamodb create-global-table --global-table-name MyTable --replication-group RegionName=us-east-1 -> Option C

4. Quick Check:

   Create Global Table = create-global-table command [OK]

Hint: Use create-global-table to make Global Tables [OK]

Common Mistakes:

• Using create-table instead of create-global-table
• Confusing update or delete commands
• Missing replication group parameter

3. Given a DynamoDB Global Table replicated in us-east-1 and eu-west-1, what happens if you write an item in us-east-1?

medium

A. The item is immediately available in eu-west-1 after replication

B. The item is only stored in us-east-1 and not replicated

C. The write fails because cross-region writes are not allowed

D. The item is stored in eu-west-1 but not in us-east-1

Solution

1. Step 1: Understand replication behavior of Global Tables

   Global Tables replicate writes made in one region to all other regions automatically and quickly.

2. Step 2: Apply to the scenario

   Writing an item in us-east-1 will replicate it to eu-west-1, making it available there.

3. Final Answer:

   The item is immediately available in eu-west-1 after replication -> Option A

4. Quick Check:

   Write in one region = replicate to others [OK]

Hint: Writes replicate automatically across regions [OK]

Common Mistakes:

• Thinking writes stay local only
• Assuming writes fail across regions
• Confusing replication direction

4. You tried to add a new region to an existing Global Table but got an error. What is a common cause?

medium

A. You forgot to enable encryption on the new region

B. The new region's table has a different primary key schema

C. Global Tables do not support more than two regions

D. You used the update-table command instead of update-global-table

Solution

1. Step 1: Check schema requirements for Global Tables

   All replicas in Global Tables must have the same primary key schema to replicate correctly.

2. Step 2: Identify cause of error

   If the new region's table has a different primary key schema, adding it will fail.

3. Final Answer:

   The new region's table has a different primary key schema -> Option B

4. Quick Check:

   Matching primary keys required for Global Tables [OK]

Hint: All regions must share the same primary key schema [OK]

Common Mistakes:

• Assuming encryption causes add-region errors
• Believing Global Tables limit regions to two
• Confusing update-table with update-global-table commands

5. You want to design a Global Table for a worldwide app with users in Asia, Europe, and America. Which strategy best reduces latency and ensures data consistency?

hard

A. Create replicas in Asia, Europe, and America with strongly consistent reads enabled

B. Create a single table in one region and route all traffic there

C. Create replicas only in Asia and America to reduce costs

D. Create replicas in Asia, Europe, and America regions with eventual consistency reads

Solution

1. Step 1: Consider latency and availability

   Replicas in all user regions reduce latency by serving data locally.

2. Step 2: Understand consistency trade-offs

   Strongly consistent reads across regions are not supported; eventual consistency is used to balance latency and consistency.

3. Step 3: Evaluate options

   Create replicas in Asia, Europe, and America regions with eventual consistency reads creates replicas in all needed regions with eventual consistency, which is best for performance and availability.

4. Final Answer:

   Create replicas in Asia, Europe, and America regions with eventual consistency reads -> Option D

5. Quick Check:

   Global Tables + eventual consistency = low latency worldwide [OK]

Hint: Use replicas in all regions with eventual consistency [OK]

Common Mistakes:

• Expecting strong consistency across regions
• Using single region causing high latency
• Skipping regions to save cost but hurting users