Demand mode
For on-demand mode table, you need to specify the intended application performs read and write throughput. DynamoDB units will follow a read request and a write request unit charge for read and write operations on the table in the application execution.
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A read request unit that the implementation of a strong consistency read request for up to 4 KB size of the project, or to perform two eventually consistent read requests. Request transaction reads two units need to read in order to perform a reading project size up to 4 KB of right. If you need to project larger than 4 KB reads, DynamoDB requires additional read requests units. Required to read the total number of units requested depending on the project size, and you need to read or eventual consistency and strong consistency read. For example, if your project size is 8 KB, you need two units in order to withstand a read request reads with strong consistency; if you choose to read eventual consistency, you need a read request unit; and for the transaction to read fetch request, the read request requires four units.
note
To learn more about DynamoDB read consistency model, see the read consistency .
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A write request unit that the implementation of the size of the project up to 1 KB write-once. If you need to write the project is greater than 1 KB, DynamoDB need to consume additional write requests units. Write request transaction requires two units in order to perform a write request is write on the size of the project up to 1 KB. The total number of units required for the write request depends on the project size. For example, if your item size is 2 KB, you need two write request unit to withstand a read request; and write request for a transaction, you need four units of write requests.
Preset mode
If you select a preset mode, specify the number of reads per second and write your application needs. You can use Auto Scaling automatically adjusts the flow rate changes according to the preset capacity of the table. This can help you in your use of DynamoDB, so that it remains at or below a defined rate request in order to obtain cost predictability.
For the preset mode table, you can read the capacity of the press unit (the RCU) and the write unit of volume (the WCU) specified throughput capacity:
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A reading unit of capacity that the implementation of a maximum size of 4 KB per second once the project reads with strong consistency, or perform twice per second reads with eventual consistency. Read request transaction requires two reading units of capacity to perform a reading of the size of the project up to 4 KB per second. If you need to project larger than 4 KB reads, DynamoDB must consume additional read capacity units. The total number of units needed to read capacity depends on the size of the project and the final consistency you need to read or reads with strong consistency. For example, if your project size is 8 KB, you need two units of read capacity to withstand a strong consistent reads per second; if you choose to read eventual consistency, you need a read capacity units; and for read request transaction, it is necessary to read four units capacity. For more information, please refer to the capacity of the unit to read consumption .
note
To learn more about DynamoDB read consistency model, see the read consistency .
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A write unit of capacity that the implementation of the write-once on the size of the project up to 1 KB per second. If you need to write the project is greater than 1 KB, DynamoDB must consume additional write capacity units. Write request transaction requires two units of write capacity to perform on the size of the write once up to 1 KB items per second. The total number of units required for the write capacity depends on the size of the project. For example, if your project size is 2 KB, you need to write two units of capacity to withstand a second read request; and write request for a transaction, you need to write four units of capacity. For more information, please refer to the capacity of the unit is written consumption .
For example, suppose you create a preset table 6 read capacity units and six units of capacity have written. Using these settings, your application can do the following:
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Strong consistency performed up to 24KB read per second (4 KB × 6 units of read capacity).
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Perform up to 48KB per second, eventually consistent read (read twice the throughput).
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Perform up to 12 KB per second transaction reads the request.
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Written per second up to 6KB (1 KB × 6 units of write capacity).
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Up to execute a transaction 3KB per second write requests.