BatchWriteItem in DynamoDB - Mini Project: Build & Apply

Batch Writing Items in DynamoDB

📖 Scenario: You are managing a small online bookstore database using DynamoDB. You want to add multiple new books to your Books table efficiently in one go.

🎯 Goal: Build a batch write request to add multiple book items to the Books table using DynamoDB's BatchWriteItem operation.

📋 What You'll Learn

Create a list of book items with exact attributes

Set up the request structure for batch writing

Use the BatchWriteItem format with PutRequest for each book

Complete the batch write request JSON structure

💡 Why This Matters

🌍 Real World

Batch writing is used in real applications to efficiently add or remove multiple items in DynamoDB with fewer network calls.

💼 Career

Understanding BatchWriteItem is important for backend developers and database engineers working with AWS DynamoDB to optimize data operations.

1

Create the list of book items

Create a variable called books as a list containing these exact dictionaries representing books: {"ISBN": "978-0132350884", "Title": "Clean Code", "Author": "Robert C. Martin"}, {"ISBN": "978-0201616224", "Title": "The Pragmatic Programmer", "Author": "Andrew Hunt"}, and {"ISBN": "978-0131103627", "Title": "The C Programming Language", "Author": "Brian W. Kernighan"}.

DynamoDB

# Create the list of book items called books
# Your code here

Hint

Use a list with dictionaries for each book. Each dictionary must have keys ISBN, Title, and Author with the exact values.

2

Set the table name for batch write

Create a variable called table_name and set it to the string "Books".

DynamoDB

books = [
    {"ISBN": "978-0132350884", "Title": "Clean Code", "Author": "Robert C. Martin"},
    {"ISBN": "978-0201616224", "Title": "The Pragmatic Programmer", "Author": "Andrew Hunt"},
    {"ISBN": "978-0131103627", "Title": "The C Programming Language", "Author": "Brian W. Kernighan"}
]
# Create a variable called table_name and set it to "Books"
# Your code here

Hint

Just assign the string "Books" to the variable table_name.

3

Build the batch write request items

Create a variable called request_items as a dictionary with the key as table_name and the value as a list of dictionaries. Each dictionary in the list should have a key PutRequest whose value is another dictionary with key Item set to the corresponding book dictionary from books. Use a list comprehension with books to build this structure.

DynamoDB

books = [
    {"ISBN": "978-0132350884", "Title": "Clean Code", "Author": "Robert C. Martin"},
    {"ISBN": "978-0201616224", "Title": "The Pragmatic Programmer", "Author": "Andrew Hunt"},
    {"ISBN": "978-0131103627", "Title": "The C Programming Language", "Author": "Brian W. Kernighan"}
]
table_name = "Books"
# Create request_items dictionary for BatchWriteItem with PutRequest for each book
# Your code here

Hint

Use a dictionary with table_name as key and a list comprehension to create PutRequest dictionaries for each book.

4

Complete the BatchWriteItem request structure

Create a variable called batch_write_request as a dictionary with the key RequestItems set to the request_items dictionary.

DynamoDB

books = [
    {"ISBN": "978-0132350884", "Title": "Clean Code", "Author": "Robert C. Martin"},
    {"ISBN": "978-0201616224", "Title": "The Pragmatic Programmer", "Author": "Andrew Hunt"},
    {"ISBN": "978-0131103627", "Title": "The C Programming Language", "Author": "Brian W. Kernighan"}
]
table_name = "Books"
request_items = {
    table_name: [
        {"PutRequest": {"Item": book}} for book in books
    ]
}
# Create batch_write_request dictionary with key 'RequestItems' set to request_items
# Your code here

Hint

Wrap the request_items dictionary inside another dictionary with key RequestItems.

Practice

1.

What is the main purpose of the BatchWriteItem operation in DynamoDB?

easy

A. To create a new table in DynamoDB

B. To read multiple items from different tables

C. To add or delete multiple items in a single request

D. To update a single item with new attributes

Solution

1. Step 1: Understand BatchWriteItem functionality

   The BatchWriteItem operation allows you to write (add or delete) multiple items in one request to save time and reduce network calls.

2. Step 2: Compare options with BatchWriteItem purpose

   Only To add or delete multiple items in a single request correctly describes adding or deleting multiple items in one request, which matches BatchWriteItem's purpose.

3. Final Answer:

   To add or delete multiple items in a single request -> Option C

4. Quick Check:

   BatchWriteItem = add/delete many items [OK]

Hint: BatchWriteItem = batch add or delete items [OK]

Common Mistakes:

• Confusing BatchWriteItem with BatchGetItem
• Thinking it updates items instead of add/delete
• Assuming it creates tables

2.

Which of the following is the correct structure for a BatchWriteItem request in DynamoDB?

{
  "RequestItems": {
    "TableName": [
      { "PutRequest": { "Item": { ... } } },
      { "DeleteRequest": { "Key": { ... } } }
    ]
  }
}

easy

A. RequestItems is an array of table names with PutRequest and DeleteRequest inside

B. RequestItems contains table names as keys and arrays of PutRequest or DeleteRequest objects as values

C. RequestItems is a list of items without specifying table names

D. RequestItems only accepts PutRequest objects, not DeleteRequest

Solution

1. Step 1: Review BatchWriteItem request format

   The RequestItems key maps table names to arrays of write requests, each being either PutRequest or DeleteRequest.

2. Step 2: Match options to correct format

   RequestItems contains table names as keys and arrays of PutRequest or DeleteRequest objects as values correctly describes the structure: table names as keys, arrays of PutRequest/DeleteRequest as values.

3. Final Answer:

   RequestItems contains table names as keys and arrays of PutRequest or DeleteRequest objects as values -> Option B

4. Quick Check:

   RequestItems = table name keys + Put/Delete arrays [OK]

Hint: RequestItems keys are table names with Put/Delete arrays [OK]

Common Mistakes:

• Using array of table names instead of object with table keys
• Omitting DeleteRequest option
• Not nesting PutRequest/DeleteRequest inside arrays

3.

Given the following BatchWriteItem request, what will be the result if one item fails due to exceeding provisioned throughput?

{
  "RequestItems": {
    "Products": [
      { "PutRequest": { "Item": { "ID": { "S": "101" }, "Name": { "S": "Pen" } } } },
      { "PutRequest": { "Item": { "ID": { "S": "102" }, "Name": { "S": "Notebook" } } } }
    ]
  }
}

medium

A. The entire batch fails and no items are written

B. The request throws a syntax error

C. Both items are written regardless of failure

D. Only the failed item is returned in UnprocessedItems for retry

Solution

1. Step 1: Understand BatchWriteItem error handling

   If some items exceed provisioned throughput, DynamoDB returns those items in UnprocessedItems for retry, not failing the entire batch.

2. Step 2: Analyze the given scenario

   One item fails due to throughput, so only that item is unprocessed and returned for retry, while others succeed.

3. Final Answer:

   Only the failed item is returned in UnprocessedItems for retry -> Option D

4. Quick Check:

   UnprocessedItems = failed items for retry [OK]

Hint: Failed items appear in UnprocessedItems for retry [OK]

Common Mistakes:

• Assuming all items fail if one fails
• Thinking BatchWriteItem throws syntax error on throughput issues
• Believing all items succeed regardless of errors

4.

Identify the error in this BatchWriteItem request snippet:

{
  "RequestItems": {
    "Orders": [
      { "PutRequest": { "Item": { "OrderId": "123", "Amount": 50 } } }
    ]
  }
}

medium

A. The attribute values are missing DynamoDB data types

B. The table name should be an array, not an object

C. PutRequest should be outside the array

D. BatchWriteItem cannot write to Orders table

Solution

1. Step 1: Check attribute value format in BatchWriteItem

   DynamoDB requires attribute values to specify data types like {"S": "string"} or {"N": "number"} in BatchWriteItem requests.

2. Step 2: Identify the error in the snippet

   Attributes "OrderId" and "Amount" lack data type wrappers, so the request is invalid.

3. Final Answer:

   The attribute values are missing DynamoDB data types -> Option A

4. Quick Check:

   Attribute values need data types like {"S": "text"} [OK]

Hint: Attribute values must include DynamoDB data types [OK]

Common Mistakes:

• Omitting data types for attribute values
• Misunderstanding table name structure
• Placing PutRequest incorrectly

5.

You want to write 50 items to a DynamoDB table using BatchWriteItem. Since the API limits 25 items per batch, how should you handle this in your application?

hard

A. Split the 50 items into two batches of 25 and retry unprocessed items after each batch

B. Send all 50 items in one BatchWriteItem request and expect it to succeed

C. Write items one by one using PutItem to avoid batch limits

D. Use BatchGetItem instead to write multiple items

Solution

1. Step 1: Recognize BatchWriteItem limits

   BatchWriteItem supports a maximum of 25 items per request, so 50 items must be split into multiple batches.

2. Step 2: Implement batching and retry logic

   Split 50 items into two batches of 25 each. After each batch, check UnprocessedItems and retry those to ensure all items are written.

3. Final Answer:

   Split the 50 items into two batches of 25 and retry unprocessed items after each batch -> Option A

4. Quick Check:

   BatchWriteItem max 25 items; split and retry [OK]

Hint: Split items into max 25 per batch and retry unprocessed [OK]

Common Mistakes:

• Sending more than 25 items in one batch
• Ignoring unprocessed items and not retrying
• Using BatchGetItem to write items