Time to live (TTL) for expiration in AWS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ service_behavior

intermediate

How does TTL affect item expiration in DynamoDB?

In AWS DynamoDB, when you enable TTL on a table, what happens to items after their TTL timestamp passes?

A Items become inaccessible but remain in the table until manually deleted.

B Items are marked for expiration and typically deleted within 48 hours after the TTL timestamp.

C Items are archived automatically to S3 when TTL expires.

D Items are immediately deleted from the table as soon as the TTL timestamp is reached.

💡 Hint

Think about how AWS handles background cleanup for expired items.

DynamoDB TTL marks items for expiration and deletes them asynchronously, usually within 48 hours after the TTL timestamp passes. Items are not deleted immediately.

❓ Configuration

intermediate

Which DynamoDB attribute type is required for TTL?

When configuring TTL on a DynamoDB table, which attribute type must the TTL attribute have?

A Number representing Unix epoch time in seconds.

B Boolean indicating if the item should expire.

C Binary data representing a timestamp.

D String representing a date in ISO 8601 format.

💡 Hint

TTL expects a timestamp in a numeric format.

The TTL attribute must be a Number type containing the Unix epoch time in seconds when the item should expire.

❓ security

advanced

What IAM permission is required to enable TTL on a DynamoDB table?

To enable TTL on a DynamoDB table using AWS IAM, which permission must be granted?

A dynamodb:UpdateTimeToLive

B dynamodb:EnableTTL

C dynamodb:ModifyTableTTL

D dynamodb:SetTTLAttribute

💡 Hint

Check the exact IAM action name for TTL updates.

The correct IAM permission to enable or disable TTL on a DynamoDB table is dynamodb:UpdateTimeToLive.

❓ Architecture

advanced

How does TTL impact read capacity and storage costs in DynamoDB?

Consider a DynamoDB table with TTL enabled. How does TTL affect read capacity units (RCUs) and storage costs over time?

A TTL reduces both storage costs and RCUs immediately after expiration.

B TTL increases RCUs because it triggers additional read operations for expired items.

C TTL reduces storage costs by deleting expired items, but does not reduce RCUs since expired items are still read until deleted.

D TTL has no effect on storage costs or RCUs.

💡 Hint

Think about when items are actually removed and how reads behave before deletion.

TTL deletes expired items asynchronously, reducing storage costs once deleted. However, until deletion, expired items still consume read capacity when accessed.

✅ Best Practice

expert

What is the recommended approach to handle TTL attribute updates for item renewal?

You want to extend the life of an item in a DynamoDB table with TTL enabled by updating its expiration time. What is the best practice to update the TTL attribute?

A Delete the item and recreate it with a new TTL attribute value.

B Leave the TTL attribute unchanged; DynamoDB automatically extends TTL on item access.

C Set the TTL attribute to null to disable expiration, then set it again to a new timestamp.

D Update the TTL attribute with a new future Unix epoch time using an atomic update operation.

💡 Hint

Consider how to safely change the expiration time without losing the item.

The recommended way to renew TTL is to update the TTL attribute with a new future timestamp atomically. Deleting or nullifying the attribute is unnecessary and can cause data loss or unintended expiration.