TTL use cases (sessions, logs, cache) in DynamoDB - Mini Project: Build & Apply

Managing Data Expiry with TTL in DynamoDB

📖 Scenario: You are building a web application that needs to manage user sessions, store logs, and cache data efficiently. To keep your database clean and performant, you want to automatically remove old or expired data using DynamoDB's TTL (Time To Live) feature.

🎯 Goal: Learn how to set up DynamoDB tables with TTL attributes for sessions, logs, and cache data to automatically expire and delete items after a certain time.

📋 What You'll Learn

Create a DynamoDB table named Sessions with a TTL attribute called expires_at.

Create a DynamoDB table named Logs with a TTL attribute called log_expiry.

Create a DynamoDB table named Cache with a TTL attribute called cache_expiry.

Insert sample items into each table with appropriate TTL timestamps.

Enable TTL on each table using the correct TTL attribute.

💡 Why This Matters

🌍 Real World

TTL helps automatically remove expired sessions, logs, and cache data, keeping your database clean and reducing storage costs.

💼 Career

Understanding TTL in DynamoDB is essential for backend developers and cloud engineers managing scalable, cost-effective applications.

1

Create DynamoDB tables with TTL attributes

Create three DynamoDB tables named Sessions, Logs, and Cache. Each table should have a primary key called id (string). Add a TTL attribute to each table: expires_at for Sessions, log_expiry for Logs, and cache_expiry for Cache. Use the AWS CLI commands exactly as shown below.

DynamoDB

# Create Sessions table with TTL attribute expires_at
# Create Logs table with TTL attribute log_expiry
# Create Cache table with TTL attribute cache_expiry

Need a hint?

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

2

Insert sample items with TTL timestamps

Insert one sample item into each table with the exact id values: session1 for Sessions, log1 for Logs, and cache1 for Cache. Add the TTL attribute with a Unix epoch timestamp in the future: expires_at = 1893456000 for Sessions, log_expiry = 1893456000 for Logs, and cache_expiry = 1893456000 for Cache. Use the AWS CLI put-item command exactly as shown.

DynamoDB

aws dynamodb create-table --table-name Sessions --attribute-definitions AttributeName=id,AttributeType=S --key-schema AttributeName=id,KeyType=HASH --billing-mode PAY_PER_REQUEST
aws dynamodb create-table --table-name Logs --attribute-definitions AttributeName=id,AttributeType=S --key-schema AttributeName=id,KeyType=HASH --billing-mode PAY_PER_REQUEST
aws dynamodb create-table --table-name Cache --attribute-definitions AttributeName=id,AttributeType=S --key-schema AttributeName=id,KeyType=HASH --billing-mode PAY_PER_REQUEST

# Insert sample item into Sessions with id 'session1' and expires_at 1893456000
# Insert sample item into Logs with id 'log1' and log_expiry 1893456000
# Insert sample item into Cache with id 'cache1' and cache_expiry 1893456000

Need a hint?

Use the AWS CLI put-item command with JSON syntax for the item attributes.

3

Enable TTL on each DynamoDB table

Enable TTL on the Sessions table using the attribute expires_at. Enable TTL on the Logs table using the attribute log_expiry. Enable TTL on the Cache table using the attribute cache_expiry. Use the AWS CLI update-time-to-live command exactly as shown below.

DynamoDB

aws dynamodb create-table --table-name Sessions --attribute-definitions AttributeName=id,AttributeType=S --key-schema AttributeName=id,KeyType=HASH --billing-mode PAY_PER_REQUEST
aws dynamodb create-table --table-name Logs --attribute-definitions AttributeName=id,AttributeType=S --key-schema AttributeName=id,KeyType=HASH --billing-mode PAY_PER_REQUEST
aws dynamodb create-table --table-name Cache --attribute-definitions AttributeName=id,AttributeType=S --key-schema AttributeName=id,KeyType=HASH --billing-mode PAY_PER_REQUEST

aws dynamodb put-item --table-name Sessions --item '{"id": {"S": "session1"}, "expires_at": {"N": "1893456000"}}'
aws dynamodb put-item --table-name Logs --item '{"id": {"S": "log1"}, "log_expiry": {"N": "1893456000"}}'
aws dynamodb put-item --table-name Cache --item '{"id": {"S": "cache1"}, "cache_expiry": {"N": "1893456000"}}'

# Enable TTL on Sessions table with attribute expires_at
# Enable TTL on Logs table with attribute log_expiry
# Enable TTL on Cache table with attribute cache_expiry

Need a hint?

Use the AWS CLI update-time-to-live command with --time-to-live-specification to enable TTL.

4

Verify TTL settings and data expiry

Write AWS CLI commands to describe the TTL status for each table: Sessions, Logs, and Cache. Use the describe-time-to-live command exactly as shown below to confirm TTL is enabled with the correct attribute names.

DynamoDB

aws dynamodb create-table --table-name Sessions --attribute-definitions AttributeName=id,AttributeType=S --key-schema AttributeName=id,KeyType=HASH --billing-mode PAY_PER_REQUEST
aws dynamodb create-table --table-name Logs --attribute-definitions AttributeName=id,AttributeType=S --key-schema AttributeName=id,KeyType=HASH --billing-mode PAY_PER_REQUEST
aws dynamodb create-table --table-name Cache --attribute-definitions AttributeName=id,AttributeType=S --key-schema AttributeName=id,KeyType=HASH --billing-mode PAY_PER_REQUEST

aws dynamodb put-item --table-name Sessions --item '{"id": {"S": "session1"}, "expires_at": {"N": "1893456000"}}'
aws dynamodb put-item --table-name Logs --item '{"id": {"S": "log1"}, "log_expiry": {"N": "1893456000"}}'
aws dynamodb put-item --table-name Cache --item '{"id": {"S": "cache1"}, "cache_expiry": {"N": "1893456000"}}'

aws dynamodb update-time-to-live --table-name Sessions --time-to-live-specification Enabled=true,AttributeName=expires_at
aws dynamodb update-time-to-live --table-name Logs --time-to-live-specification Enabled=true,AttributeName=log_expiry
aws dynamodb update-time-to-live --table-name Cache --time-to-live-specification Enabled=true,AttributeName=cache_expiry

# Describe TTL status for Sessions table
# Describe TTL status for Logs table
# Describe TTL status for Cache table

Need a hint?

Use the AWS CLI describe-time-to-live command to check TTL status.