TTL behavior and timing in DynamoDB - Mini Project: Build & Apply

Understanding TTL Behavior and Timing in DynamoDB

📖 Scenario: You are managing a DynamoDB table that stores user session data. To keep the table clean and efficient, you want to automatically remove expired sessions using DynamoDB's Time To Live (TTL) feature.

🎯 Goal: Build a DynamoDB table setup with TTL enabled on a specific attribute, configure the TTL attribute values, and understand how TTL expiration timing works.

📋 What You'll Learn

Create a DynamoDB table named UserSessions with a primary key SessionId (string).

Add a TTL attribute named ExpirationTime to the table items.

Set the TTL attribute ExpirationTime with Unix epoch timestamps for session expiration.

Enable TTL on the ExpirationTime attribute in the table configuration.

Understand that TTL deletion is approximate and can take up to 48 hours after expiration.

💡 Why This Matters

🌍 Real World

TTL helps automatically remove expired data like sessions, logs, or temporary records to save storage and improve performance.

💼 Career

Understanding TTL is important for database administrators and backend developers managing data lifecycle and cost optimization in DynamoDB.

1

Create the DynamoDB table with primary key

Create a DynamoDB table named UserSessions with a primary key called SessionId of type string.

DynamoDB

# Create the DynamoDB table UserSessions with primary key SessionId (string)
# Your code here

Need a hint?

Use the AWS CLI create-table command with --attribute-definitions and --key-schema to define the primary key.

2

Add TTL attribute to items

Add an item to the UserSessions table with SessionId set to session123 and a TTL attribute called ExpirationTime set to the Unix epoch timestamp 1700000000.

DynamoDB

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

# Add an item with SessionId 'session123' and ExpirationTime 1700000000
# Your code here

Need a hint?

Use the AWS CLI put-item command to add an item with the TTL attribute as a number.

3

Enable TTL on the ExpirationTime attribute

Enable TTL on the UserSessions table by setting the TTL attribute name to ExpirationTime using the AWS CLI.

DynamoDB

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

aws dynamodb put-item \
    --table-name UserSessions \
    --item '{"SessionId": {"S": "session123"}, "ExpirationTime": {"N": "1700000000"}}'

# Enable TTL on the ExpirationTime attribute
# Your code here

Need a hint?

Use the AWS CLI update-time-to-live command to enable TTL on the table.

4

Understand TTL expiration timing

Add a comment explaining that DynamoDB TTL deletion is approximate and can take up to 48 hours after the ExpirationTime timestamp to delete expired items.

DynamoDB

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

aws dynamodb put-item \
    --table-name UserSessions \
    --item '{"SessionId": {"S": "session123"}, "ExpirationTime": {"N": "1700000000"}}'

aws dynamodb update-time-to-live \
    --table-name UserSessions \
    --time-to-live-specification Enabled=true,AttributeName=ExpirationTime

# Add a comment about TTL deletion timing
# Your code here

Need a hint?

Write a comment explaining the approximate nature of TTL deletion timing.