Transactions

5 minutes 5 Questions

Amazon DynamoDB supports transactions, which enable you to perform multiple create, update, or delete operations in a single request. DynamoDB transactions provide the following guarantees: all-or-nothing (all operations within a transaction succeed or fail as a group), isolation (no other requests can modify the affected items while a transaction is in progress), and consistency (the items affected by the transaction must be in a consistent state before the transaction starts and after it finishes). Transactions simplify complex business logic and help maintain data integrity by ensuring that multiple, related operations are performed atomically and in the correct order. You can use transactions for scenarios such as transferring funds between accounts, updating multiple tables, or inserting multiple related items in a few steps.

Guide to Amazon DynamoDB Transactions

Importance:
Transactions in Amazon DynamoDB are important as they provide developers with a mechanism to maintain data correctness in applications by adding atomicity and isolation to DynamoDB. They are used to handle complex business logic that requires multiple, unrelated actions.

What is DynamoDB Transactions?:
Amazon DynamoDB Transactions enables developers to group multiple actions across one or more tables into a single, all-or-nothing operation. It is tailored to meet ACID (Atomicity, Consistency, Isolation, Durability) properties, which helps in maintaining data integrity.

How does DynamoDB Transactions work?:
The transactional read and write operations of DynamoDB, namely TransactWriteItems and TransactGetItems, bundle multiple steps into a single interaction, improving code clarity and making error handling more straightforward. If a condition in the TransactWriteItems operation fails, then the entire transaction fails and none of the changes are reflected.

Exam Tips on Answering Questions on Transactions:
1. Brush up your understanding of ACID properties.
2. Get a thorough grip on the functions and benefits of TransactGetItems and TransactWriteItems operations.
3. Review different scenarios where transactions should be used, such as when you need to ensure that multiple items in multiple tables are updated together.
4. Remember DynamoDB transactions can't span regions or get locked when they are in progress.

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Question 1

An online shopping platform requires transaction support for multiple items being purchased at once. Which AWS service should be used to ensure transactional support for multi-item orders?

Amazon S3 with Object Lock Amazon Simple Notification Service (SNS) Amazon DynamoDB with AWS Lambda Amazon RDS with Read Replicas

Correct Answer: Amazon DynamoDB with AWS Lambda

Amazon DynamoDB with AWS Lambda allows for multiple-item transactions to be processed and ensures transactional support. The other options do not provide the transactional support required for multi-item purchases.

Question 2

A finance company requires high-availability for their SQL transactional database. Which of the following AWS database solutions provides automatic failover with a Multi-AZ deployment?

Amazon RDS Amazon Redshift Amazon ElastiCache Amazon Aurora

Correct Answer: Amazon RDS

Amazon RDS supports automatic failover with a Multi-AZ deployment, providing high-availability for SQL transactional databases. While Aurora also provides this feature, it was not listed as a correct answer, since it is a part of Amazon RDS.

Question 3

A company runs a financial application that processes transactions. During peak hours, the application's capacity to handle transactions is exceeded, causing some transactions to fail. What is the appropriate solution?

Migrate the application to a larger EC2 instance. Use Amazon SQS to decouple the application and store transactions temporarily. Use a NAT Gateway to handle the increased number of transactions. Enable Amazon S3 versioning to store additional transactions.

Correct Answer: Use Amazon SQS to decouple the application and store transactions temporarily.

By using Amazon SQS, the application can store transactions temporarily, which can then be processed by the application during non-peak hours, avoiding failure due to capacity constraints. The other options do not address the capacity limitation during peak hours.

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