How to Use TTL for Session Management in DynamoDB

Use DynamoDB's Time To Live (TTL) feature by adding a timestamp attribute that marks when a session should expire. DynamoDB automatically deletes items after the TTL timestamp passes, making it ideal for managing session lifetimes without manual cleanup.

Syntax

To enable TTL for session management, add a numeric attribute to your DynamoDB items that stores the expiration time as a Unix epoch timestamp (in seconds). Then, enable TTL on your table specifying this attribute.

• TTLAttributeName: The name of the attribute holding the expiration timestamp.
• ExpirationTime: Unix epoch time in seconds when the item should expire.

bash

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

Output

An output confirming TTL is enabled on the table with the specified attribute.

Example

This example shows how to insert a session item with an expiration time 30 minutes from now, so DynamoDB will delete it automatically after that.

python

import time
import boto3

dynamodb = boto3.resource('dynamodb')
table = dynamodb.Table('Sessions')

# Current time plus 30 minutes (1800 seconds)
expiration_time = int(time.time()) + 1800

# Put session item with TTL attribute
response = table.put_item(
    Item={
        'SessionId': 'session123',
        'UserId': 'user456',
        'ExpirationTime': expiration_time
    }
)
print('PutItem succeeded:', response)

Output

PutItem succeeded: {'ResponseMetadata': {'RequestId': '...', 'HTTPStatusCode': 200, ...}}

Common Pitfalls

• TTL attribute must be a number representing Unix epoch time in seconds; strings or other formats won't work.
• TTL deletion is not immediate; DynamoDB typically deletes expired items within 48 hours.
• Do not rely on TTL for critical immediate deletion; use it for eventual cleanup.
• Ensure TTL is enabled on the table and the attribute name matches exactly.

none

## Wrong: Using string timestamp
# Item with 'ExpirationTime': '2024-06-01T12:00:00Z' will NOT expire

## Right: Use Unix epoch seconds
# 'ExpirationTime': 1710000000

Quick Reference

Summary tips for using TTL in DynamoDB session management:

• Store expiration as Unix epoch seconds in a numeric attribute.
• Enable TTL on your table with that attribute name.
• Set expiration time when creating or updating session items.
• Expect eventual deletion, not immediate.
• Use TTL to reduce manual cleanup of expired sessions.

Key Takeaways

Enable TTL on your DynamoDB table specifying a numeric expiration attribute.

Store session expiration as Unix epoch time in seconds in each session item.

DynamoDB deletes expired items automatically but not instantly; expect some delay.

Use TTL to automate cleanup of expired sessions and reduce manual maintenance.

Ensure the TTL attribute is correctly named and formatted as a number for TTL to work.