Cost estimation for access patterns in DynamoDB - Step-by-Step Execution

Concept Flow - Cost estimation for access patterns

Start: Define Access Pattern

↓

Identify Read/Write Type

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Calculate Units Needed

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Multiply by Operation Count

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Sum Total Units

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Estimate Cost Based on Units

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End

This flow shows how to estimate DynamoDB costs by defining access patterns, calculating read/write units, and summing them to find total cost.

Execution Sample

DynamoDB

ReadCapacityUnits = 5
WriteCapacityUnits = 2
ReadsPerSecond = 10
WritesPerSecond = 4
TotalReadUnits = ReadsPerSecond * ReadCapacityUnits
TotalWriteUnits = WritesPerSecond * WriteCapacityUnits
TotalUnits = TotalReadUnits + TotalWriteUnits

Calculates total read and write capacity units consumed per second based on access pattern.

Execution Table

Step	Variable	Value	Calculation/Action	Explanation
1	ReadCapacityUnits	5	Defined	Set read units per operation
2	WriteCapacityUnits	2	Defined	Set write units per operation
3	ReadsPerSecond	10	Defined	Number of read operations per second
4	WritesPerSecond	4	Defined	Number of write operations per second
5	TotalReadUnits	50	10 * 5	Total read units consumed per second
6	TotalWriteUnits	8	4 * 2	Total write units consumed per second
7	TotalUnits	58	50 + 8	Sum of read and write units
8	CostEstimation	$X	TotalUnits * UnitPrice	Multiply units by price per unit

💡 Calculation ends after total units and cost estimation are computed.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	After Step 5	After Step 6	Final
ReadCapacityUnits	undefined	5	5	5	5	5	5	5
WriteCapacityUnits	undefined	undefined	2	2	2	2	2	2
ReadsPerSecond	undefined	undefined	undefined	10	10	10	10	10
WritesPerSecond	undefined	undefined	undefined	undefined	4	4	4	4
TotalReadUnits	undefined	undefined	undefined	undefined	undefined	50	50	50
TotalWriteUnits	undefined	undefined	undefined	undefined	undefined	undefined	8	8
TotalUnits	undefined	undefined	undefined	undefined	undefined	undefined	undefined	58

Key Moments - 3 Insights

Why do we multiply ReadsPerSecond by ReadCapacityUnits?

Because each read operation consumes a certain number of capacity units, multiplying gives total units consumed per second (see execution_table row 5).

What happens if WritesPerSecond increases?

TotalWriteUnits will increase proportionally, raising TotalUnits and cost (see execution_table rows 6 and 7).

Why do we sum TotalReadUnits and TotalWriteUnits?

Because total consumed capacity is the sum of read and write units, which determines overall cost (see execution_table row 7).

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of TotalReadUnits at step 5?

A 10

B 5

C 50

D 58

💡 Hint

Check the 'Value' column at step 5 in the execution_table.

At which step is TotalUnits calculated?

A Step 6

B Step 7

C Step 4

D Step 8

💡 Hint

Look for the step where TotalUnits is assigned in the execution_table.

If WritesPerSecond doubles, what happens to TotalWriteUnits?

A It doubles

B It stays the same

C It halves

D It becomes zero

💡 Hint

Refer to how TotalWriteUnits is calculated in execution_table row 6.

Concept Snapshot

Cost estimation in DynamoDB:
- Define read/write capacity units per operation
- Multiply by number of operations per second
- Sum read and write units for total
- Multiply total units by unit price for cost
- Adjust for access pattern changes

Full Transcript

This visual execution trace shows how to estimate DynamoDB costs based on access patterns. We start by defining the read and write capacity units per operation, then specify how many read and write operations happen each second. We multiply these to find total read and write units consumed per second. Adding these gives total capacity units used. Finally, multiplying total units by the price per unit estimates the cost. This step-by-step calculation helps understand how access patterns affect DynamoDB costs.