Time to live (TTL) for expiration in AWS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to enable TTL on a DynamoDB table.

AWS

aws dynamodb update-time-to-live --table-name MyTable --time-to-live-specification Enabled=[1],AttributeName=ttl

Drag options to blanks, or click blank then click option'

Atrue

Bfalse

Cenabled

Dyes

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'enabled' or 'yes' instead of true

Setting Enabled to false disables TTL

TTL must be enabled by setting Enabled to true.

2fill in blank

medium

Complete the code to specify the TTL attribute name in DynamoDB.

AWS

aws dynamodb update-time-to-live --table-name MyTable --time-to-live-specification Enabled=true,AttributeName=[1]

Drag options to blanks, or click blank then click option'

Aexpiration

BtimeToLive

Cttl

Dexpiry

Attempts:

3 left

💡 Hint

Common Mistakes

Using attribute names not defined in the table

Using incorrect casing or spelling

The TTL attribute name is commonly set to 'ttl' in DynamoDB.

3fill in blank

hard

Fix the error in the TTL configuration command.

AWS

aws dynamodb update-time-to-live --table-name MyTable --time-to-live-specification Enabled=[1],AttributeName=ttl

Drag options to blanks, or click blank then click option'

Atrue

BTrue

C'true'

DTRUE

Attempts:

3 left

💡 Hint

Common Mistakes

Using uppercase or quoted true

Using string values instead of boolean

The value for Enabled must be lowercase true without quotes.

4fill in blank

hard

Fill both blanks to create a TTL attribute in a DynamoDB item.

AWS

item = {'id': '123', 'name': 'test', '[1]': [2]

Drag options to blanks, or click blank then click option'

Attl

Bexpiration

C1672531199

D2023-12-31T23:59:59Z

Attempts:

3 left

💡 Hint

Common Mistakes

Using date strings instead of epoch timestamps

Using wrong attribute names

The TTL attribute name is 'ttl' and its value is a Unix timestamp like 1672531199.

5fill in blank

hard

Fill all three blanks to configure TTL in a CloudFormation template.

AWS

"Resources": {
  "MyTable": {
    "Type": "AWS::DynamoDB::Table",
    "Properties": {
      "TableName": "MyTable",
      "AttributeDefinitions": [
        {"AttributeName": "id", "AttributeType": "S"},
        {"AttributeName": "[1]", "AttributeType": "N"}
      ],
      "KeySchema": [
        {"AttributeName": "id", "KeyType": "HASH"}
      ],
      "TimeToLiveSpecification": {
        "Enabled": [2],
        "AttributeName": "[3]"
      }
    }
  }
}

Drag options to blanks, or click blank then click option'

Attl

Btrue

Dexpiration

Attempts:

3 left

💡 Hint

Common Mistakes

Using different attribute names in definitions and TTL spec

Setting Enabled to false or a string

The TTL attribute is named 'ttl', enabled is true, and the attribute name in TTL spec is 'ttl'.

Practice

1. What is the main purpose of Time to Live (TTL) in AWS DynamoDB?

easy

A. Backup data to another region

B. Encrypt data at rest for security

C. Automatically delete expired items to save storage space

D. Increase read capacity for faster queries

Solution

1. Step 1: Understand TTL function

   TTL is designed to remove items automatically after a set expiration time.

2. Step 2: Identify the main benefit

   This automatic deletion helps save storage space and reduces manual cleanup.

3. Final Answer:

   Automatically delete expired items to save storage space -> Option C

4. Quick Check:

   TTL purpose = automatic deletion [OK]

Hint: TTL deletes expired data automatically to save space [OK]

Common Mistakes:

• Confusing TTL with encryption
• Thinking TTL backs up data
• Assuming TTL improves query speed

2. Which attribute type must the TTL attribute have in DynamoDB to enable expiration?

easy

A. Number representing Unix epoch time in seconds

B. Binary data with expiration timestamp

C. Boolean indicating expired or not

D. String containing date in ISO format

Solution

1. Step 1: Check TTL attribute requirements

   DynamoDB TTL requires a Number attribute representing expiration time as Unix epoch seconds.

2. Step 2: Eliminate other types

   String, Boolean, or Binary types are not valid for TTL expiration timestamps.

3. Final Answer:

   Number representing Unix epoch time in seconds -> Option A

4. Quick Check:

   TTL attribute = Number (epoch seconds) [OK]

Hint: TTL attribute must be a number with epoch seconds [OK]

Common Mistakes:

• Using string dates instead of numbers
• Setting TTL attribute as Boolean
• Trying to use binary data for TTL

3. Given this DynamoDB item with TTL attribute expireAt: 1700000000 (Unix epoch seconds), what happens when current time is 1700000001?

medium

A. Item remains until manually deleted

B. Item's TTL attribute is reset to current time

C. Item is archived to S3 automatically

D. Item is immediately deleted by DynamoDB TTL process

Solution

1. Step 1: Compare current time with TTL value

   The current time (1700000001) is greater than the TTL attribute (1700000000), so the item is expired.

2. Step 2: Understand TTL behavior on expiration

   DynamoDB TTL automatically deletes expired items shortly after expiration time passes.

3. Final Answer:

   Item is immediately deleted by DynamoDB TTL process -> Option D

4. Quick Check:

   Current time > TTL = item deleted [OK]

Hint: Item deletes soon after TTL time passes [OK]

Common Mistakes:

• Thinking TTL deletes instantly at exact second
• Assuming manual deletion is needed
• Believing TTL archives data instead of deleting

4. You enabled TTL on attribute expiry but items are not deleting after expiration. What is the most likely cause?

medium

A. DynamoDB table is in a different region

B. TTL attribute expiry is missing or has wrong data type

C. TTL only works on primary key attributes

D. TTL requires manual activation every 24 hours

Solution

1. Step 1: Check TTL attribute correctness

   If the TTL attribute is missing or not a Number with epoch seconds, TTL won't delete items.

2. Step 2: Verify other options

   TTL works regardless of region, does not require manual activation, and does not need to be primary key.

3. Final Answer:

   TTL attribute expiry is missing or has wrong data type -> Option B

4. Quick Check:

   Wrong TTL attribute = no deletion [OK]

Hint: TTL attribute must exist and be correct type [OK]

Common Mistakes:

• Thinking TTL depends on table region
• Believing TTL needs manual daily activation
• Assuming TTL attribute must be primary key

5. You want to store session data that expires exactly 30 minutes after creation using DynamoDB TTL. Which approach correctly sets the TTL attribute?

hard

A. Set TTL attribute to current Unix epoch time in seconds plus 1800 seconds

B. Set TTL attribute to current time as ISO string plus 30 minutes

C. Set TTL attribute to Boolean true when session expires

D. Set TTL attribute to current Unix epoch time in milliseconds plus 1800000

Solution

1. Step 1: Calculate TTL value correctly

   TTL attribute must be a Number in seconds, so add 1800 seconds (30 minutes) to current epoch seconds.

2. Step 2: Eliminate incorrect formats

   ISO strings, Booleans, or milliseconds are invalid for TTL attribute in DynamoDB.

3. Final Answer:

   Set TTL attribute to current Unix epoch time in seconds plus 1800 seconds -> Option A

4. Quick Check:

   TTL = epoch seconds + 1800 [OK]

Hint: TTL value = current epoch seconds + 1800 for 30 minutes [OK]

Common Mistakes:

• Using ISO date strings instead of epoch seconds
• Using milliseconds instead of seconds
• Setting TTL as Boolean instead of number