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    <blockquote> <p>If I pay for 10 "read units" which allows for 10 highly consistent reads per second, will I be throttled if I try to do 20 reads in a single second, even if it was the only 20 reads that occurred in the last hour?</p> </blockquote> <p>Yes, this is due to the very concept of <a href="http://aws.amazon.com/dynamodb/">Amazon DynamoDB</a> being <em>fast and predictable performance with seamless scalability</em> - the quoted FAQ is actually addressing this correctly already (i.e. you have to take operations/second literally), though the calculation is better illustrated in <a href="http://docs.amazonwebservices.com/amazondynamodb/latest/developerguide/ProvisionedThroughputIntro.html">Provisioned Throughput in Amazon DynamoDB</a> indeed:</p> <blockquote> <p><strong>A unit of Write Capacity</strong> enables you to perform <strong>one write per second for items of up to 1KB in size</strong>. Similarly, <strong>a unit of Read Capacity</strong> enables you to perform <strong>one strongly consistent read per second (or two eventually consistent reads per second) of items of up to 1KB in size.</strong> Larger items will require more capacity. You can calculate the number of units of read and write capacity you need by estimating the number of reads or writes you need to do per second and multiplying by the size of your items (rounded up to the nearest KB).</p> <p>Units of Capacity required for writes = Number of item writes per second x item size (rounded up to the nearest KB) </p> <p>Units of Capacity required for reads* = Number of item reads per second x item size (rounded up to the nearest KB) * <em>If you use eventually consistent reads you’ll get twice the throughput in terms of reads per second.</em></p> <p><em>[emphasis mine]</em></p> </blockquote> <p>Getting these calculations right for real world use cases is potentially complex though, please make sure to check further details like e.g. the <a href="http://docs.amazonwebservices.com/amazondynamodb/latest/developerguide/BestPractices.html">Provisioned Throughput Guidelines in Amazon DynamoDB</a> as well accordingly.</p>
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    1. POHow is Amazon DynamoDB throughput calculated and limited?
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    1. USSteffen Opel
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    1. COI read the information you quote above on the AWS site before asking the question, and I still find the text to be ambiguous. It also seems illogical to me that it would be literally calculated each second, since that would mean that you would always have to substantially over-provision to accomodate any possible short burst or suffer the consequences of getting HTTP 400 error responses for the extra reads/writes.
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      1. USBrian McKelvey
    2. COIMO, the only way this service makes any sense would be for it to be at least a little bit "burstable." The pricing for this really ought to work similarly to the way data centers charge for bandwidth... i.e. 95th percentile billing.
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    3. COHave you actually tested it and know for certain that it is strictly limited, second by second, or is that just the way you interpret their posted information?
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