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Timestamp writes for write hedging in Amazon DynamoDB
- The article discusses how to enforce client-side timestamp-based write sequence order on Amazon DynamoDB to prevent lower timestamps from overwriting higher ones even with out-of-order requests or retries.
- By using timestamp-based write sequencing, where each write includes a ConditionExpression checking new item timestamp against existing item, the article ensures correct write order.
- The post explains using hedging techniques for faster read latencies and how the same concept can be applied to write requests, ensuring that subsequent writes are treated based on the initial timestamp.
- It highlights the importance of timestamp attributes for each item to decide write validity time, even in scenarios like data stream processing or SDK retries.
- Deletion handling involves utilizing tombstones to mark soft deletes, with an example demonstrating how to handle deletions effectively.
- The article provides a Python code sample for performing PutItem with conditional expressions to manage write order based on timestamps.
- It emphasizes the importance of managing tombstones and utilizing TTL attribute for orchestrating deletions in a DynamoDB table.
- The technique is applicable for PutItem and DeleteItem operations but not for BatchWriteItem due to lack of condition support, and UpdateItem can be used cautiously based on the item section being updated.
- Cost analysis suggests minimal additional cost with this design, emphasizing accurate timestamp values and mitigating clock skew for reliable write sequence enforcement.
- In conclusion, the article provides a comprehensive guide on leveraging timestamp attributes and condition expressions in DynamoDB for maintaining write sequence integrity and handling deletions efficiently.
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