Transaction limits in DynamoDB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the maximum number of items you can include in a single DynamoDB transaction?

You can include up to 100 items in a single DynamoDB transaction.

beginner

What is the maximum size limit for a single item in a DynamoDB transaction?

Each item in a DynamoDB transaction can be up to 400 KB in size.

beginner

True or False: DynamoDB transactions can span multiple tables.

True. DynamoDB transactions can include operations on multiple tables within the same AWS account and region.

intermediate

What is the maximum total size of all items in a single DynamoDB transaction?

The total size of all items in a single DynamoDB transaction cannot exceed 4 MB.

intermediate

Why is it important to keep transaction size limits in mind when designing DynamoDB operations?

Because exceeding transaction limits causes the transaction to fail, which can affect application reliability and performance.

What is the maximum number of operations allowed in a single DynamoDB transaction?

A 25

B 100

C 50

D 10

DynamoDB transactions support up to 100 operations per transaction.

What is the maximum size of a single item in a DynamoDB transaction?

A 400 KB

B 2 MB

C 256 KB

D 1 MB

Each item in a DynamoDB transaction can be up to 400 KB in size.

Can a DynamoDB transaction include operations on multiple tables?

A No, only one table per transaction

B Yes, but only if tables are in different regions

C Yes, if tables are in the same AWS account and region

D No, transactions are limited to a single partition key

DynamoDB transactions can include multiple tables within the same AWS account and region.

What happens if a DynamoDB transaction exceeds the size or item count limits?

A The transaction fails and no changes are applied

B Only the first 25 items are processed

C The transaction is automatically split

D The transaction is queued for later processing

If transaction limits are exceeded, the entire transaction fails and no changes are made.

What is the maximum total size of all items in a single DynamoDB transaction?

A 10 MB

B 2 MB

C 1 MB

D 4 MB

The total size of all items in a single DynamoDB transaction cannot exceed 4 MB.

Explain the key transaction limits in DynamoDB and why they matter.

Think about item count, item size, total size, and multi-table support.

Describe what happens if a DynamoDB transaction exceeds its limits during execution.

Consider the atomic nature of transactions.

Practice

1. What is the maximum number of operations allowed in a single TransactWriteItems request in DynamoDB?

easy

A. 50 operations

B. 25 operations

C. 5 operations

D. 10 operations

Solution

1. Step 1: Understand DynamoDB transaction limits

   DynamoDB limits the number of operations in a transaction to ensure performance and consistency.

2. Step 2: Recall the specific limit for TransactWriteItems

   The limit for TransactWriteItems is 10 operations per transaction.

3. Final Answer:

   10 operations -> Option D

4. Quick Check:

   TransactWriteItems max ops = 10 [OK]

Hint: Remember: Write transactions allow up to 10 ops only [OK]

Common Mistakes:

• Confusing write and read transaction limits
• Assuming more than 10 operations are allowed in write transactions
• Mixing up TransactWriteItems with TransactGetItems limits

2. Which of the following is the correct syntax to start a transaction with multiple write operations in DynamoDB using TransactWriteItems?

easy

A. dynamodb.transactWriteItems({ Items: [...] })

B. dynamodb.transactWriteItems({ TransactItems: [...] })

C. dynamodb.transactWrite({ Operations: [...] })

D. dynamodb.transactWrite({ Items: [...] })

Solution

1. Step 1: Identify the correct parameter name for transaction items

   The DynamoDB API for TransactWriteItems requires the parameter TransactItems to specify operations.

2. Step 2: Match the syntax with the correct parameter

   Only dynamodb.transactWriteItems({ TransactItems: [...] }) uses TransactItems correctly inside the method call.

3. Final Answer:

   dynamodb.transactWriteItems({ TransactItems: [...] }) -> Option B

4. Quick Check:

   Use TransactItems for write transactions [OK]

Hint: Look for 'TransactItems' key in write transaction syntax [OK]

Common Mistakes:

• Using 'Items' instead of 'TransactItems'
• Calling a non-existent method like 'transactWrite'
• Confusing parameter names for transaction operations

3. Consider a DynamoDB transaction using TransactGetItems with 30 get operations. What will happen when this transaction is executed?

medium

A. The transaction fails because it exceeds the 25 operation limit

B. The transaction succeeds and returns all 30 items

C. Only the first 25 items are returned, others ignored

D. The transaction partially succeeds with a warning

Solution

1. Step 1: Recall the operation limit for TransactGetItems

   DynamoDB limits TransactGetItems to a maximum of 25 operations per transaction.

2. Step 2: Analyze the effect of exceeding the limit

   Submitting 30 operations exceeds this limit, causing the entire transaction to fail.

3. Final Answer:

   The transaction fails because it exceeds the 25 operation limit -> Option A

4. Quick Check:

   TransactGetItems max ops = 25 [OK]

Hint: TransactGetItems max 25 ops; more causes failure [OK]

Common Mistakes:

• Assuming partial success with extra operations
• Thinking the limit is 30 or more
• Believing the transaction truncates results automatically

4. You wrote a DynamoDB transaction with 12 write operations inside TransactWriteItems. The transaction fails. What is the most likely cause?

medium

A. Exceeded the maximum of 25 operations allowed in TransactWriteItems

B. Exceeded the maximum size of 4 MB per item

C. Exceeded the maximum of 10 operations allowed in TransactWriteItems

D. Used incorrect parameter name 'Items' instead of 'TransactItems'

Solution

1. Step 1: Check the operation count limit for TransactWriteItems

   The maximum allowed operations in TransactWriteItems is 10.

2. Step 2: Identify the cause of failure with 12 operations

   Since 12 exceeds 10, the transaction fails due to exceeding the operation limit.

3. Final Answer:

   Exceeded the maximum of 10 operations allowed in TransactWriteItems -> Option C

4. Quick Check:

   More than 10 ops in write transaction causes failure [OK]

Hint: More than 10 writes in transaction causes failure [OK]

Common Mistakes:

• Confusing operation count with item size limits
• Assuming 25 ops limit applies to write transactions
• Ignoring parameter name errors as cause

5. You want to perform a transaction that reads 20 items and writes 8 items atomically in DynamoDB. How should you structure your requests to stay within transaction limits?

hard

A. Use one TransactWriteItems with 8 writes and one TransactGetItems with 20 reads separately

B. Use a single TransactWriteItems with 28 operations combining reads and writes

C. Use one TransactGetItems with 20 reads and add 8 writes to it

D. Use a single TransactGetItems with 28 operations combining reads and writes

Solution

1. Step 1: Understand separate transaction types and their limits

   DynamoDB separates read and write transactions: TransactWriteItems for writes (max 10 ops), TransactGetItems for reads (max 25 ops).

2. Step 2: Plan transactions to respect limits

   Perform writes (8 ops) in one TransactWriteItems and reads (20 ops) in one TransactGetItems to stay within limits.

3. Final Answer:

   Use one TransactWriteItems with 8 writes and one TransactGetItems with 20 reads separately -> Option A

4. Quick Check:

   Separate read/write transactions to respect limits [OK]

Hint: Split reads and writes into separate transactions [OK]

Common Mistakes:

• Trying to combine reads and writes in one transaction
• Exceeding operation limits by mixing types
• Assuming one transaction can handle both reads and writes