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Cloud Computing · Advanced

DynamoDB Capacity Modes

DynamoDB billing options: on-demand (pay per request) or provisioned (set read and write capacity units, optionally auto scaled).

Definition

In provisioned mode, one read capacity unit (RCU) supports one strongly consistent read per second (or two eventually consistent) of up to 4 KB, and one write capacity unit (WCU) supports one write per second of up to 1 KB. On-demand mode charges per request and instantly accommodates traffic changes. Reserved capacity discounts apply to provisioned mode.

Example

Writing 10 items per second of 3 KB each requires 30 WCUs in provisioned mode.

Exam tip

Expect RCU/WCU calculations: round item size up to 4 KB for reads and 1 KB for writes; eventually consistent reads cost half.

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