Put, get, and query operations in AWS - Mini Project: Build & Apply

Put, get, and query operations

📖 Scenario: You are building a simple cloud database to store and retrieve user profiles. Each profile has a unique user ID, a name, and an email address. You will create the data structure, configure a key for queries, add data, and then retrieve data using put, get, and query operations.

🎯 Goal: Build a simple AWS DynamoDB table setup with put, get, and query operations to store and retrieve user profiles by user ID.

📋 What You'll Learn

Create a DynamoDB table named UserProfiles with UserID as the primary key

Add a configuration variable for the table name

Write a put operation to add a user profile with UserID, Name, and Email

Write a get operation to retrieve a user profile by UserID

Write a query operation to find user profiles by UserID

💡 Why This Matters

🌍 Real World

Cloud databases like DynamoDB are used to store user data for web and mobile apps. Knowing how to put, get, and query data is essential for building responsive applications.

💼 Career

These operations are fundamental skills for cloud engineers, backend developers, and anyone working with AWS cloud services.

1

Create DynamoDB table data structure

Create a dictionary called table_definition that defines a DynamoDB table named UserProfiles with a primary key attribute called UserID of type string.

AWS

# Your code here

Hint

Think of table_definition as a blueprint for your database table. You need to specify the table name and the key structure.

2

Add configuration variable for table name

Create a variable called table_name and set it to the string 'UserProfiles'.

AWS

table_definition = {
    'TableName': 'UserProfiles',
    'KeySchema': [
        {'AttributeName': 'UserID', 'KeyType': 'HASH'}
    ],
    'AttributeDefinitions': [
        {'AttributeName': 'UserID', 'AttributeType': 'S'}
    ],
    'ProvisionedThroughput': {
        'ReadCapacityUnits': 5,
        'WriteCapacityUnits': 5
    }
}
# Your code here

Hint

This variable will help you refer to the table easily in your code.

3

Write put operation to add a user profile

Write a dictionary called put_item that represents a DynamoDB put operation to add a user profile with UserID set to 'user123', Name set to 'Alice', and Email set to '[e-mail]'.

AWS

table_definition = {
    'TableName': 'UserProfiles',
    'KeySchema': [
        {'AttributeName': 'UserID', 'KeyType': 'HASH'}
    ],
    'AttributeDefinitions': [
        {'AttributeName': 'UserID', 'AttributeType': 'S'}
    ],
    'ProvisionedThroughput': {
        'ReadCapacityUnits': 5,
        'WriteCapacityUnits': 5
    }
}
table_name = 'UserProfiles'
# Your code here

Hint

Use the Item key to specify the data you want to add. Each attribute needs its type specified as 'S' for string.

4

Write get and query operations to retrieve user profile

Write two dictionaries: get_item to get a user profile by UserID set to 'user123', and query_item to query the table for items where UserID equals 'user123'.

AWS

table_definition = {
    'TableName': 'UserProfiles',
    'KeySchema': [
        {'AttributeName': 'UserID', 'KeyType': 'HASH'}
    ],
    'AttributeDefinitions': [
        {'AttributeName': 'UserID', 'AttributeType': 'S'}
    ],
    'ProvisionedThroughput': {
        'ReadCapacityUnits': 5,
        'WriteCapacityUnits': 5
    }
}
table_name = 'UserProfiles'
put_item = {
    'TableName': table_name,
    'Item': {
        'UserID': {'S': 'user123'},
        'Name': {'S': 'Alice'},
        'Email': {'S': '[e-mail]'}
    }
}
# Your code here

Hint

Use Key for get operations and KeyConditionExpression with ExpressionAttributeValues for query operations.

Practice

1. What does the put operation do in AWS DynamoDB?

easy

A. Saves or updates an item in the table

B. Retrieves a single item by its key

C. Searches items based on key conditions

D. Deletes an item from the table

Solution

1. Step 1: Understand the purpose of put

   The put operation is used to save a new item or update an existing item in a DynamoDB table.

2. Step 2: Compare with other operations

   get retrieves one item by key, query searches by key conditions, and delete removes an item.

3. Final Answer:

   Saves or updates an item in the table -> Option A

4. Quick Check:

   Put = Save or update [OK]

Hint: Put means save or update data [OK]

Common Mistakes:

• Confusing put with get or query
• Thinking put deletes data
• Assuming put only adds new items

2. Which of the following is the correct syntax to get an item by its key in AWS SDK for JavaScript DynamoDB client?

easy

A. dynamoDBClient.put({ TableName: 'MyTable', Item: { id: '123' } })

B. dynamoDBClient.get({ TableName: 'MyTable', Key: { id: '123' } })

C. dynamoDBClient.query({ TableName: 'MyTable', KeyConditionExpression: 'id = :id' })

D. dynamoDBClient.getItem({ TableName: 'MyTable', Key: { id: '123' } })

Solution

1. Step 1: Identify the correct method for getting an item

   The AWS SDK for JavaScript v3 uses get method on the DynamoDB DocumentClient to retrieve a single item by key.

2. Step 2: Check the parameters

   The parameters include TableName and Key with the key attribute and value.

3. Final Answer:

   dynamoDBClient.get({ TableName: 'MyTable', Key: { id: '123' } }) -> Option B

4. Quick Check:

   Get item uses get() with TableName and Key [OK]

Hint: Get single item uses get() with Key [OK]

Common Mistakes:

• Using getItem() instead of get()
• Confusing query with get
• Using put() to get data

3. Given this DynamoDB query code snippet, what will be the output if the table contains items with userId 'user1' and 'user2' only?

const params = {
  TableName: 'Users',
  KeyConditionExpression: 'userId = :uid',
  ExpressionAttributeValues: { ':uid': 'user1' }
};
const result = await dynamoDBClient.query(params);
console.log(result.Items);

medium

A. [{ userId: 'user2', name: 'Bob' }]

B. []

C. [{ userId: 'user1', name: 'Alice' }]

D. Error: Missing Key

Solution

1. Step 1: Understand the query parameters

   The query searches for items where userId equals 'user1'.

2. Step 2: Match items in the table

   Since the table has 'user1' and 'user2', only the item with 'user1' matches and is returned.

3. Final Answer:

   [{ userId: 'user1', name: 'Alice' }] -> Option C

4. Quick Check:

   Query filters by key condition, returns matching items [OK]

Hint: Query returns items matching key condition [OK]

Common Mistakes:

• Expecting all items returned
• Confusing query with scan
• Thinking query returns error without full key

4. You wrote this code to get an item but it throws an error:

const params = {
  TableName: 'Products',
  Key: { productId: 101 }
};
const data = await dynamoDBClient.getItem(params);
console.log(data.Item);

What is the likely cause of the error?

medium

A. The key attribute value must be a string, not a number

B. The method should be get instead of getItem

C. Missing KeyConditionExpression in parameters

D. TableName is incorrect

Solution

1. Step 1: Check the key attribute type

   DynamoDB keys must be typed as attribute values, usually strings or objects with type wrappers.

2. Step 2: Identify the error cause

   Passing a plain number (101) without type wrapper causes a validation error.

3. Final Answer:

   The key attribute value must be a string, not a number -> Option A

4. Quick Check:

   Key values need correct type format [OK]

Hint: Key values must be strings or typed attributes [OK]

Common Mistakes:

• Using wrong method name
• Missing KeyConditionExpression in getItem
• Incorrect table name

5. You want to update a user's email in DynamoDB only if the user exists. Which operation and condition should you use?

hard

A. Use query to find the user, then put to update

B. Use get to check existence, then put to update

C. Use put without any condition

D. Use put with a condition expression checking attribute_exists(userId)

Solution

1. Step 1: Understand conditional update

   To update only if the user exists, use put with a condition expression that checks for the user's existence.

2. Step 2: Use attribute_exists condition

   The condition attribute_exists(userId) ensures the item exists before updating, preventing overwriting non-existing items.

3. Final Answer:

   Use put with a condition expression checking attribute_exists(userId) -> Option D

4. Quick Check:

   Conditional put prevents overwriting missing items [OK]

Hint: Use put with condition attribute_exists() to update safely [OK]

Common Mistakes:

• Using get then put causes race conditions
• Using query unnecessarily for single item
• Putting without condition overwrites blindly