A developer's application uses an Amazon DynamoDB table with a local secondary index (LSI). During testing the table returns ProvisionedThroughputExceededException errors, even though the test suite's request rate did not exceed the table's overall provisioned capacity. What is the most likely cause?

The most likely cause is that the table's partition key values are not evenly distributed across partitions. DynamoDB distributes data and traffic based on the partition key. If a few partition key values receive a disproportionately high number of requests, those specific partitions can become "hot," leading to ProvisionedThroughputExceededException errors even if the overall table capacity isn't fully utilized. This is because the capacity is shared across partitions. Incorrect options: LSIs share the same provisioned capacity as their base table, so a different capacity is not the issue. While exponential backoff is a best practice for retries, it addresses transient errors and doesn't prevent hot partitions from occurring in the first place. IAM permissions issues would result in access denied errors, not ProvisionedThroughputExceededException.