SHA256
29 lines
679 B
Markdown
29 lines
679 B
Markdown
# Read / Write Capacity Units
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This is for [[_DynamoDB|DynamoDB]].
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## Writing
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Math goes sort of like this:
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$$
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\begin{aligned}
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w &= \text{write} \\
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tw &= \text{transactional write} \\
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\ \\
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1\ WCU &= 1\ kb/w/s \\
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2\ WCU &= 1\ kb/tw/s \\
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\end{aligned}
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$$
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Take away is that a 1KB write is 1WCU. And a 1KB [transactional]{.underline} write is 2WCU.
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## Reading
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The math for reading is a little bit more convoluted, because the reads are divided by 4KB blocks.
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$$
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\begin{aligned}
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cr &= \text{consistent read} \\
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ecr &= \text{eventually consistent read} \\
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tr &= \text{transactional read} \\
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\ \\
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1\ RCU &= 4kb/cr/s \\
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\frac{1}{2}\ RCU &= 4kb/ecr/s \\
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2 RCU &= 4kb/tr/s
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\end{aligned}
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$$
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