Sparse index pattern in DynamoDB - Mini Project: Build & Apply

Implementing Sparse Index Pattern in DynamoDB

📖 Scenario: You are building a DynamoDB table to store user profiles. Some users have premium subscriptions, and you want to efficiently query only premium users without scanning the entire table.

🎯 Goal: Create a DynamoDB table with a sparse index that allows querying only premium users efficiently.

📋 What You'll Learn

Create a DynamoDB table named UserProfiles with UserID as the primary key.

Add an attribute SubscriptionType with values either "premium" or "free".

Create a sparse Global Secondary Index (GSI) named PremiumUsersIndex that indexes only items where SubscriptionType is "premium".

Write a query to retrieve all premium users using the sparse index.

💡 Why This Matters

🌍 Real World

Sparse indexes help optimize queries in DynamoDB by indexing only a subset of items, reducing costs and improving performance when filtering on specific attributes.

💼 Career

Understanding sparse indexes is important for database engineers and backend developers working with DynamoDB to design efficient, scalable data models.

1

Create the DynamoDB table with user profiles

Create a DynamoDB table named UserProfiles with UserID as the partition key. Add sample items with UserID and SubscriptionType attributes. Include at least one user with SubscriptionType set to "premium" and one with "free".

DynamoDB

# Create the UserProfiles table with UserID as the primary key
# Add sample items with UserID and SubscriptionType

Need a hint?

Define a list named UserProfiles with dictionaries for each user. Include UserID and SubscriptionType keys.

2

Define the sparse index configuration

Create a variable named PremiumUsersIndex that represents a sparse Global Secondary Index (GSI) configuration. It should have IndexName set to "PremiumUsersIndex", PartitionKey set to "UserID", and a FilterExpression that includes only items where SubscriptionType equals "premium".

DynamoDB

UserProfiles = [
    {"UserID": "user1", "SubscriptionType": "premium"},
    {"UserID": "user2", "SubscriptionType": "free"},
    {"UserID": "user3", "SubscriptionType": "premium"},
    {"UserID": "user4", "SubscriptionType": "free"}
]

# Define the PremiumUsersIndex sparse index configuration

Need a hint?

Create a dictionary named PremiumUsersIndex with keys IndexName, PartitionKey, and FilterExpression filtering for "premium" subscription type.

3

Write the query to get premium users using the sparse index

Write a query expression named query_premium_users that uses the PremiumUsersIndex to retrieve all items where SubscriptionType is "premium". Use the IndexName from PremiumUsersIndex and the filter expression with the value :premium set to "premium".

DynamoDB

UserProfiles = [
    {"UserID": "user1", "SubscriptionType": "premium"},
    {"UserID": "user2", "SubscriptionType": "free"},
    {"UserID": "user3", "SubscriptionType": "premium"},
    {"UserID": "user4", "SubscriptionType": "free"}
]

PremiumUsersIndex = {
    "IndexName": "PremiumUsersIndex",
    "PartitionKey": "UserID",
    "FilterExpression": "SubscriptionType = :premium",
    "ExpressionAttributeValues": {":premium": "premium"}
}

# Write the query expression to get premium users

Need a hint?

Create a dictionary named query_premium_users using the IndexName from PremiumUsersIndex and set the KeyConditionExpression to filter for "premium" subscription type.

4

Complete the sparse index pattern setup

Add a final configuration line to the UserProfiles items to include the SubscriptionType attribute only for premium users, making the index sparse. This means only items with SubscriptionType set to "premium" should have this attribute.

DynamoDB

UserProfiles = [
    {"UserID": "user1", "SubscriptionType": "premium"},
    {"UserID": "user2", "SubscriptionType": "free"},
    {"UserID": "user3", "SubscriptionType": "premium"},
    {"UserID": "user4", "SubscriptionType": "free"}
]

PremiumUsersIndex = {
    "IndexName": "PremiumUsersIndex",
    "PartitionKey": "UserID",
    "FilterExpression": "SubscriptionType = :premium",
    "ExpressionAttributeValues": {":premium": "premium"}
}

query_premium_users = {
    "IndexName": PremiumUsersIndex["IndexName"],
    "KeyConditionExpression": "SubscriptionType = :premium",
    "ExpressionAttributeValues": {":premium": "premium"}
}

# Remove SubscriptionType attribute from free users to make the index sparse

Need a hint?

Remove the SubscriptionType attribute from users with free subscriptions so only premium users have this attribute, making the index sparse.