Why automatic expiration manages data lifecycle in DynamoDB - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to enable automatic expiration on a DynamoDB table by specifying the TTL attribute.

DynamoDB

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'

AExpirationTime

BDeleteAt

CTTL

DExpireOn

Attempts:

3 left

💡 Hint

Common Mistakes

Using attribute names like 'ExpirationTime' or 'DeleteAt' which are not recognized by DynamoDB TTL.

The TTL attribute must be named exactly as specified when enabling automatic expiration. 'TTL' is the common attribute name used for this purpose.

2fill in blank

medium

Complete the code to query items that have not yet expired by filtering on the TTL attribute.

DynamoDB

SELECT * FROM MyTable WHERE [1] > unixTimestamp(CURRENT_TIMESTAMP)

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

ADeleteAt

BTTL

CExpirationTime

DExpireOn

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect attribute names that do not match the TTL attribute.

To find items that are still valid, you compare the TTL attribute to the current time. The TTL attribute is used for this purpose.

3fill in blank

hard

Fix the error in the TTL configuration command by selecting the correct option for enabling TTL.

DynamoDB

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 capitalized or quoted boolean values causing syntax errors.

The 'Enabled' field expects a lowercase boolean string 'true' without quotes in the AWS CLI command.

4fill in blank

hard

Fill both blanks to create a DynamoDB table with TTL enabled on the 'TTL' attribute.

DynamoDB

aws dynamodb create-table --table-name MyTable --attribute-definitions AttributeName=ID,AttributeType=S --key-schema AttributeName=ID,KeyType=HASH --billing-mode PAY_PER_REQUEST --[1] Enabled=true,AttributeName=[2]

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

Atime-to-live-specification

Btime-to-live

Cttl

Dttl-specification

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect parameter names like 'ttl' or 'ttl-specification' which are invalid.

The correct parameter to enable TTL is 'time-to-live-specification' and the attribute name is 'ttl'.

5fill in blank

hard

Fill all three blanks to write a DynamoDB expression that deletes expired items based on the TTL attribute.

DynamoDB

DELETE FROM MyTable WHERE [1] <= unixTimestamp([2]) AND [3] = true

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

ATTL

BCURRENT_TIMESTAMP

CisExpired

DExpirationFlag

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect attribute names or missing the expiration flag condition.

The TTL attribute stores the expiration time. We compare it to the current timestamp. The 'isExpired' flag can be used to mark expired items.

Practice

1. What is the main benefit of using automatic expiration (TTL) in DynamoDB to manage data lifecycle?

easy

A. It requires manual deletion of expired items.

B. It increases the storage size of the table.

C. It automatically deletes expired data without manual intervention.

D. It slows down query performance.

Solution

1. Step 1: Understand TTL purpose in DynamoDB

   TTL (Time To Live) is designed to automatically remove items after a set expiration time.

2. Step 2: Identify the benefit of automatic expiration

   This automatic removal means no manual cleanup is needed, reducing maintenance effort.

3. Final Answer:

   It automatically deletes expired data without manual intervention. -> Option C

4. Quick Check:

   Automatic deletion = It automatically deletes expired data without manual intervention. [OK]

Hint: TTL auto-removes expired data, no manual cleanup needed [OK]

Common Mistakes:

• Thinking TTL increases storage size
• Assuming manual deletion is still required
• Believing TTL slows down queries

2. Which of the following is the correct way to define a TTL attribute in a DynamoDB item?

easy

A. { "ttl": 1717262400 }

B. { "ttl": "2024-06-01T12:00:00Z" }

C. { "ttl": true }

D. { "ttl": "expired" }

Solution

1. Step 1: Recall TTL attribute format

   TTL requires a Unix epoch time (number of seconds since Jan 1, 1970) as a number.

2. Step 2: Identify correct TTL value type

   { "ttl": 1717262400 } uses a numeric Unix epoch timestamp, which is correct for TTL.

3. Final Answer:

   { "ttl": 1717262400 } -> Option A

4. Quick Check:

   TTL = Unix epoch number [OK]

Hint: TTL must be a Unix epoch number, not string or boolean [OK]

Common Mistakes:

• Using ISO date string instead of Unix epoch
• Setting TTL as boolean true
• Using non-numeric strings for TTL

3. Given the following DynamoDB item with TTL set to 1717262400 (Unix epoch time), what happens after that time passes?

{ "id": "123", "data": "sample", "ttl": 1717262400 }

medium

A. The item is automatically deleted by DynamoDB.

B. The item causes an error when TTL expires.

C. The item is archived but not deleted.

D. The item remains in the table indefinitely.

Solution

1. Step 1: Understand TTL expiration effect

   When the current time passes the TTL timestamp, DynamoDB marks the item for deletion.

2. Step 2: Identify DynamoDB behavior on expired items

   DynamoDB automatically deletes expired items without user action.

3. Final Answer:

   The item is automatically deleted by DynamoDB. -> Option A

4. Quick Check:

   TTL expiry triggers auto-deletion [OK]

Hint: Expired TTL items get auto-deleted by DynamoDB [OK]

Common Mistakes:

• Thinking items stay forever after TTL
• Assuming items are archived instead of deleted
• Believing TTL expiration causes errors

4. You set a TTL attribute on your DynamoDB table items, but expired items are not being deleted. What is the most likely cause?

medium

A. The TTL attribute is set as a string instead of a number.

B. The TTL feature is not enabled on the table.

C. The table has no primary key defined.

D. The items have no attribute named 'ttl'.

Solution

1. Step 1: Check TTL feature activation

   TTL must be enabled on the DynamoDB table to work; just setting attribute is not enough.

2. Step 2: Identify common misconfiguration

   If TTL is not enabled, expired items will not be deleted automatically.

3. Final Answer:

   The TTL feature is not enabled on the table. -> Option B

4. Quick Check:

   TTL must be enabled on table [OK]

Hint: Enable TTL on table, not just set attribute [OK]

Common Mistakes:

• Assuming TTL works without enabling it
• Confusing attribute type with feature activation
• Ignoring missing TTL attribute on items

5. You want to keep user session data in DynamoDB but automatically remove sessions older than 24 hours. Which approach best uses automatic expiration to manage this lifecycle?

hard

A. Manually scan and delete sessions older than 24 hours every hour.

B. Disable TTL and rely on application logic to remove old sessions.

C. Store session expiration as a string date and delete manually.

D. Add a TTL attribute with the session creation time plus 86400 seconds (24 hours).

Solution

1. Step 1: Calculate TTL for session expiration

   TTL should be set as Unix epoch time when the session expires, i.e., creation time + 86400 seconds.

2. Step 2: Use DynamoDB TTL to automate deletion

   Setting TTL this way lets DynamoDB auto-delete sessions after 24 hours without manual work.

3. Final Answer:

   Add a TTL attribute with the session creation time plus 86400 seconds (24 hours). -> Option D

4. Quick Check:

   TTL = creation time + 24h seconds [OK]

Hint: TTL = creation timestamp + 86400 seconds for 24h expiry [OK]

Common Mistakes:

• Using manual deletion instead of TTL
• Storing expiration as string, not Unix epoch
• Disabling TTL and relying on app logic