DynamoDB capacity modes (on-demand, provisioned) in AWS - Step-by-Step Execution

Process Flow - DynamoDB capacity modes (on-demand, provisioned)

Start

↓

Choose Capacity Mode

↓

On-Demand

↓

Auto scales

↓

Pay per request

↓

Handle Traffic

↓

End

You start by choosing a capacity mode. On-demand mode automatically handles traffic and charges per request. Provisioned mode requires setting capacity units and monitoring usage.

Execution Sample

AWS

CreateTable(
  CapacityMode='ON_DEMAND'
)

UpdateTable(
  CapacityMode='PROVISIONED',
  ReadCapacityUnits=5,
  WriteCapacityUnits=5
)

This code creates a DynamoDB table first with on-demand mode, then updates it to provisioned mode with 5 read and write units.

Process Table

Step	Action	Capacity Mode	Read Units	Write Units	Billing	Result
1	Create table	ON_DEMAND	N/A	N/A	Pay per request	Table created with on-demand mode
2	Traffic starts	ON_DEMAND	N/A	N/A	Auto scales	Handles any traffic automatically
3	Update table	PROVISIONED	5	5	Pay per capacity unit	Table updated to provisioned mode
4	Traffic continues	PROVISIONED	5	5	Fixed capacity billing	Uses set capacity units, throttles if exceeded
5	Adjust capacity	PROVISIONED	10	10	Updated billing	Capacity units increased to handle more traffic
6	Traffic spikes beyond capacity	PROVISIONED	10	10	Throttling occurs	Requests above capacity are throttled
7	Switch back to on-demand	ON_DEMAND	N/A	N/A	Pay per request	Table switches back to on-demand mode
8	Traffic spikes	ON_DEMAND	N/A	N/A	Auto scales	Handles spikes without throttling
9	End	-	-	-	-	Capacity mode choice affects billing and scaling

💡 Execution ends after switching modes and handling traffic with different billing and scaling behaviors.

Status Tracker

Variable	Start	After Step 1	After Step 3	After Step 5	After Step 7	Final
CapacityMode	None	ON_DEMAND	PROVISIONED	PROVISIONED	ON_DEMAND	ON_DEMAND
ReadUnits	None	N/A	5	10	N/A	N/A
WriteUnits	None	N/A	5	10	N/A	N/A
Billing	None	Pay per request	Pay per capacity unit	Updated billing	Pay per request	Pay per request

Key Moments - 3 Insights

Why does the ReadUnits value show 'N/A' in on-demand mode?

In on-demand mode, you don't set read or write units because DynamoDB automatically handles capacity. This is shown in execution_table rows 1 and 2 where ReadUnits is 'N/A'.

What happens if traffic exceeds provisioned capacity units?

When traffic goes beyond provisioned units, requests get throttled as shown in step 6 of the execution_table. This means some requests are delayed or rejected until capacity is increased.

How does billing differ between on-demand and provisioned modes?

On-demand billing charges per request automatically (rows 1,2,8). Provisioned billing charges based on set capacity units regardless of usage (rows 3,4,5).

Visual Quiz - 3 Questions

Look at the execution_table, what is the CapacityMode after step 5?

A N/A

B ON_DEMAND

C PROVISIONED

D UNKNOWN

💡 Hint

Check the CapacityMode column in execution_table row for step 5.

At which step does throttling occur due to traffic exceeding capacity?

A Step 4

B Step 6

C Step 2

D Step 8

💡 Hint

Look for 'Throttling occurs' in the Result column of execution_table.

If you switch from provisioned to on-demand mode, what happens to ReadUnits and WriteUnits?

A They become N/A

B They stay the same

C They reset to zero

D They double

💡 Hint

Check variable_tracker values after step 7 for ReadUnits and WriteUnits.

Concept Snapshot

DynamoDB Capacity Modes:
- On-Demand: No capacity units set, auto scales, pay per request.
- Provisioned: Set read/write units, fixed billing, may throttle if exceeded.
- Switch modes anytime to balance cost and performance.
- Monitor usage to adjust provisioned units as needed.

Full Transcript

This visual execution shows how DynamoDB capacity modes work. You start by creating a table in on-demand mode, which automatically scales and charges per request. Then you update the table to provisioned mode, setting fixed read and write capacity units. Traffic is handled within these limits, and if exceeded, throttling occurs. You can adjust capacity units to handle more traffic. Switching back to on-demand removes capacity limits and throttling, charging per request again. The execution table tracks each step, showing capacity mode, units, billing, and results. Variable tracker shows how capacity mode and units change over time. Key moments clarify common confusions about capacity units in on-demand mode, throttling in provisioned mode, and billing differences. The quiz tests understanding of these execution steps. This helps beginners see how capacity modes affect DynamoDB behavior and cost.