AWS SDK for JavaScript/Node.js in DynamoDB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the AWS SDK for JavaScript/Node.js used for?

It is a set of tools that helps your JavaScript or Node.js app talk to AWS services like DynamoDB, S3, and more, so you can store data, upload files, and manage cloud resources easily.

beginner

How do you create a DynamoDB client using AWS SDK for JavaScript v3?

You import DynamoDBClient from '@aws-sdk/client-dynamodb' and create a new instance with configuration like region. Example: 
const { DynamoDBClient } = require('@aws-sdk/client-dynamodb');
const client = new DynamoDBClient({ region: 'us-east-1' });

beginner

What is the purpose of the 'PutItemCommand' in AWS SDK for JavaScript/Node.js?

PutItemCommand is used to add a new item or replace an existing item in a DynamoDB table. It sends the data you want to store to DynamoDB.

beginner

Why should you handle errors when calling AWS SDK methods?

Because network issues, permission problems, or wrong data can cause requests to fail. Handling errors helps your app respond gracefully and avoid crashes.

beginner

What does 'await' do when calling AWS SDK commands in Node.js?

'await' pauses your code until the AWS service responds, so you get the result directly without using complicated callbacks. It makes your code easier to read and write.

Which AWS SDK package do you import to use DynamoDB client in JavaScript v3?

A dynamodb-sdk

B aws-sdk

C @aws-sdk/dynamodb-client

D @aws-sdk/client-dynamodb

The correct package for DynamoDB client in AWS SDK for JavaScript v3 is '@aws-sdk/client-dynamodb'.

What does the 'PutItemCommand' do in DynamoDB?

A Adds or replaces an item

B Updates an attribute only

C Reads an item

D Deletes an item

PutItemCommand adds a new item or replaces an existing item in a DynamoDB table.

Why is it important to handle errors when using AWS SDK calls?

A To increase AWS costs

B To speed up the request

C To avoid app crashes and handle failures gracefully

D To ignore network issues

Handling errors helps your app avoid crashes and respond properly to problems like network failures or permission errors.

What does 'await' do in an async function when calling AWS SDK commands?

A Waits for the command to finish and returns the result

B Stops the program permanently

C Runs the command in the background

D Skips the command

'await' pauses the function until the AWS SDK command finishes and returns the result.

Which region format is correct when configuring DynamoDBClient?

A USEast1

B us-east-1

C us_east_1

D east-us-1

AWS regions use lowercase letters and hyphens, like 'us-east-1'.

Explain how to set up and use the AWS SDK for JavaScript/Node.js to put an item into a DynamoDB table.

Think about the steps from importing to sending the command and handling the response.

Describe why asynchronous programming with 'async/await' is helpful when working with AWS SDK in Node.js.

Consider how async/await changes the flow of code execution.

Practice

1. What is the first step to interact with DynamoDB using the AWS SDK for JavaScript/Node.js?

easy

A. Create a DynamoDB client instance

B. Write a SQL query

C. Install a database driver

D. Open a database connection manually

Solution

1. Step 1: Understand AWS SDK usage

   To work with DynamoDB, you first create a client object that represents the service.

2. Step 2: Recognize the role of the client

   The client handles requests and responses to DynamoDB; no manual connection or SQL is needed.

3. Final Answer:

   Create a DynamoDB client instance -> Option A

4. Quick Check:

   Client creation = First step [OK]

Hint: Always start by creating the service client [OK]

Common Mistakes:

• Trying to write SQL queries for DynamoDB
• Assuming manual connection is needed
• Skipping client creation

2. Which of the following is the correct way to import the DynamoDB client from AWS SDK v3 in Node.js?

easy

A. const DynamoDBClient = require('@aws-sdk/client-dynamodb');

B. const { DynamoDBClient } = require('aws-sdk');

C. import { DynamoDBClient } from '@aws-sdk/client-dynamodb';

D. import DynamoDBClient from 'aws-sdk';

Solution

1. Step 1: Identify AWS SDK v3 import style

   AWS SDK v3 uses ES modules and named imports from '@aws-sdk/client-dynamodb'.

2. Step 2: Match correct syntax

   import { DynamoDBClient } from '@aws-sdk/client-dynamodb'; uses ES module import with correct package and named import syntax.

3. Final Answer:

   import { DynamoDBClient } from '@aws-sdk/client-dynamodb'; -> Option C

4. Quick Check:

   ES module named import = import { DynamoDBClient } from '@aws-sdk/client-dynamodb'; [OK]

Hint: Use ES module imports from '@aws-sdk/client-dynamodb' [OK]

Common Mistakes:

• Using old AWS SDK v2 import style
• Using default import instead of named import
• Mixing require and import syntax

3. Given the following code snippet, what will be logged if the item exists in the DynamoDB table?

import { DynamoDBClient, GetItemCommand } from '@aws-sdk/client-dynamodb';
const client = new DynamoDBClient({ region: 'us-east-1' });

async function getItem() {
  const command = new GetItemCommand({
    TableName: 'Users',
    Key: { 'UserId': { S: '123' } }
  });
  const response = await client.send(command);
  console.log(response.Item);
}
getItem();

medium

A. Undefined because no item exists

B. An empty object {}

C. An error is thrown due to missing parameters

D. The item object with attributes if found

Solution

1. Step 1: Understand GetItemCommand behavior

   GetItemCommand returns an object with an Item property if the item exists.

2. Step 2: Analyze console.log output

   Logging response.Item will show the item's attributes as an object if found.

3. Final Answer:

   The item object with attributes if found -> Option D

4. Quick Check:

   response.Item = item object [OK]

Hint: GetItemCommand returns Item if found, else undefined [OK]

Common Mistakes:

• Expecting an error when item is missing
• Assuming response itself is the item
• Confusing empty object with undefined

4. What is wrong with the following code snippet that tries to put an item into DynamoDB?

import { DynamoDBClient, PutItemCommand } from '@aws-sdk/client-dynamodb';
const client = new DynamoDBClient({ region: 'us-east-1' });

async function putItem() {
  const command = new PutItemCommand({
    TableName: 'Users',
    Item: { UserId: '123', Name: 'Alice' }
  });
  await client.send(command);
}
putItem();

medium

A. TableName should be lowercase

B. Item attributes must be wrapped with DynamoDB data types like { S: 'value' }

C. PutItemCommand does not exist in AWS SDK

D. Missing await before client.send

Solution

1. Step 1: Check Item attribute format

   DynamoDB expects attribute values wrapped in type descriptors like { S: 'string' }.

2. Step 2: Identify the error cause

   Passing plain strings without type wrappers causes validation errors.

3. Final Answer:

   Item attributes must be wrapped with DynamoDB data types like { S: 'value' } -> Option B

4. Quick Check:

   Attribute values need type wrappers [OK]

Hint: Always wrap attribute values with DynamoDB types (S, N, etc.) [OK]

Common Mistakes:

• Passing plain strings instead of typed attributes
• Assuming table names are case-insensitive
• Forgetting to await async calls

5. You want to update a user's email in DynamoDB using AWS SDK for JavaScript/Node.js. Which approach correctly updates only the email attribute without overwriting the entire item?

const command = new UpdateItemCommand({
  TableName: 'Users',
  Key: { UserId: { S: '123' } },
  UpdateExpression: 'SET Email = :email',
  ExpressionAttributeValues: { ':email': { S: '[e-mail]' } }
});
await client.send(command);

hard

A. This code correctly updates only the Email attribute

B. UpdateExpression should be 'ADD Email :email' to update

C. You must use PutItemCommand to update attributes

D. ExpressionAttributeValues keys should not start with ':'

Solution

1. Step 1: Understand UpdateItemCommand usage

   UpdateExpression with 'SET' updates specified attributes without replacing the whole item.

2. Step 2: Verify ExpressionAttributeValues syntax

   Keys start with ':' and values use DynamoDB types, matching the expression.

3. Step 3: Confirm no overwrite occurs

   Using UpdateItemCommand with SET updates only Email, preserving other attributes.

4. Final Answer:

   This code correctly updates only the Email attribute -> Option A

5. Quick Check:

   UpdateExpression SET = partial update [OK]

Hint: Use UpdateItemCommand with SET to update attributes safely [OK]

Common Mistakes:

• Using PutItemCommand which overwrites entire item
• Using ADD instead of SET for attribute update
• Removing ':' prefix in ExpressionAttributeValues keys