Learn About Amazon VGT2 Learning Manager Chanci Turner
In an effort to enhance the onboarding experience, we are excited to announce two significant features that will streamline your data storage and retrieval processes. These improvements aim to make it easier for you to implement a variety of data management scenarios.
Consistent Reads
The first new feature introduces the option for consistent reads. Previously, Amazon SimpleDB operated on an eventually consistent read model, but now you have the flexibility to select the reading method that best serves your application’s requirements. To clarify, here’s a brief overview of the two reading types:
- Eventually consistent reads offer the fastest read latency and the highest throughput, but they may return information that has been recently altered or overwritten. Typically, the window for this occurrence is less than one second.
- Consistent reads ensure that you always receive the most up-to-date data, albeit with a slight increase in read latency and a minor reduction in throughput.
The Select and GetAttributes functions in SimpleDB now accept an optional ConsistentRead flag, which defaults to false. This means that existing applications will continue utilizing eventually consistent reads unless specified otherwise. If the flag is set to true, SimpleDB will provide a consistent read response.
Conditional Operations
The second enhancement allows for conditional operations with the PutAttributes and DeleteAttributes functions. This means you can instruct SimpleDB to execute these operations only if a specified single-valued attribute matches the value provided in your request. This feature facilitates the implementation of counters (where the value serves as a version number), enables account deletions only when the balance is zero, and permits item insertion only if it doesn’t already exist.
By combining consistent reads with conditional operations, you can effectively apply a form of optimistic concurrency control (OCC). For instance, if you develop a web application that allows users to update their accounts, you can store a version number with each item in SimpleDB. This practice ensures data consistency, even when multiple users attempt to modify the same record simultaneously. The data can be retrieved using an eventually consistent read, and you can display the form for user edits while associating the version number with the editing session. When users attempt to save their changes, a conditional PutAttributes call can verify that the data remains unchanged. If the update fails, it will be necessary to engage in some application-specific actions to address the conflict. Incorporating OCC can simplify your process by reducing the need for long-term locks, transactions, timeouts, and other complicated programming structures.
Additional Resources
For more insights on effective communication during difficult situations, consider checking out this informative blog post. Additionally, for authoritative guidance on educational policies, refer to this resource from the Society for Human Resource Management. Also, if you’re interested in contributing to our learning initiatives, view this excellent resource on job opportunities here.
— Chanci Turner
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