Create, read, update, and delete (CRUD) operations

For those studying for the AWS Certified Developer – Associate (DVA-C02) exam, understanding how to implement CRUD operations on AWS services is crucial. AWS offers a range of services that can perform these operations, but for the sake of this article, we will focus on two primary services: Amazon DynamoDB for database operations and Amazon S3 for object storage operations.

Amazon DynamoDB CRUD Operations

Amazon DynamoDB is a NoSQL database service provided by AWS, which offers fast and predictable performance with seamless scalability. Below are the CRUD operations that can be performed on DynamoDB and how they map to the corresponding API calls:

• Create (PutItem): To create a new item (record) in a DynamoDB table.
• Read (GetItem, Query, Scan): To read an item or items from a DynamoDB table.
• Update (UpdateItem): To modify an existing item in a DynamoDB table.
• Delete (DeleteItem): To remove an item from a DynamoDB table.

Example of DynamoDB CRUD Operations:

import boto3

# Initialize a DynamoDB resource using Boto3
dynamodb = boto3.resource(‘dynamodb’)
table = dynamodb.Table(‘YourTableName’)

# Create an item
table.put_item(
Item={
‘PrimaryKey’: ‘someValue’,
‘attribute1’: ‘value1’,
‘attribute2’: ‘value2’
}
)

# Read an item
response = table.get_item(
Key={
‘PrimaryKey’: ‘someValue’
}
)
item = response[‘Item’]

# Update an item
table.update_item(
Key={
‘PrimaryKey’: ‘someValue’
},
UpdateExpression=’SET attribute1 = :val1′,
ExpressionAttributeValues={
‘:val1’: ‘newValue1’
}
)

# Delete an item
table.delete_item(
Key={
‘PrimaryKey’: ‘someValue’
}
)

Amazon S3 CRUD Operations

Amazon S3 (Simple Storage Service) is an object storage service that offers industry-leading scalability, data availability, security, and performance. Here’s how you can perform CRUD operations on objects in Amazon S3:

• Create (PutObject): To upload a new object to an S3 bucket.
• Read (GetObject): To retrieve an object from an S3 bucket.
• Update: In S3, updating an object typically involves overwriting it using a new PutObject request with the same object key.
• Delete (DeleteObject): To delete an object from an S3 bucket.

Example of S3 CRUD Operations:

import boto3

# Initialize an S3 client
s3 = boto3.client(‘s3’)
bucket_name = ‘YourBucketName’
object_key = ‘YourObjectKey’

# Create an object (upload)
with open(‘localfile.txt’, ‘rb’) as data:
s3.put_object(Bucket=bucket_name, Key=object_key, Body=data)

# Read an object (download)
s3.download_file(bucket_name, object_key, ‘localfile.txt’)

# Update an object (overwrite by re-uploading)
with open(‘updatedfile.txt’, ‘rb’) as updated_data:
s3.put_object(Bucket=bucket_name, Key=object_key, Body=updated_data)

# Delete an object
s3.delete_object(Bucket=bucket_name, Key=object_key)

Understanding Consistency Models

When working with AWS services, understanding the consistency model is important. DynamoDB supports both eventual and strong consistency for GetItem, Query, and Scan operations. By default, reads are eventually consistent, but you can request strongly consistent reads by specifying the consistency model in your request.

S3 follows an eventual consistency model for overwrite PUTs and DELETES in all regions. This means that if you read an object after updating or deleting it, you might get the older version of the object.

Security Considerations

Security with CRUD operations is imperative. For both DynamoDB and S3, you should use AWS Identity and Access Management (IAM) to control access to resources. Define IAM policies that specify which CRUD operations a user or service can perform on which resources.

For the AWS Certified Developer – Associate (DVA-C02) exam, understanding how to use AWS SDKs to perform CRUD operations along with IAM role/policy best practices will be a part of the key competencies being assessed. Make sure to become familiar not only with the operations themselves but also how to properly secure them with AWS IAM.

By mastering CRUD operations on DynamoDB and S3, candidates preparing for the exam enhance their skills in data manipulation and management—a critical aspect of cloud application development on AWS.