Table capacity modes (on-demand vs provisioned) in DynamoDB - Visual Side-by-Side Comparison

Concept Flow - Table capacity modes (on-demand vs provisioned)

Start

↓

Choose Capacity Mode

↓

On-Demand Mode

↓

Auto scales

↓

Pay per request

↓

Handle Traffic

↓

End

You start by choosing a capacity mode: on-demand auto-scales and charges per request, while provisioned requires setting fixed read/write units and paying for them.

Execution Sample

DynamoDB

CREATE TABLE MyTable (
  id STRING HASH KEY
) CAPACITY_MODE ON_DEMAND;

This creates a DynamoDB table with on-demand capacity mode, which automatically adjusts to traffic.

Execution Table

Step	Action	Capacity Mode	Read Capacity Units (RCU)	Write Capacity Units (WCU)	Billing	Result
1	Create table with ON_DEMAND mode	ON_DEMAND	Auto	Auto	Pay per request	Table created with on-demand capacity
2	Traffic increases	ON_DEMAND	Auto scales up	Auto scales up	Charges increase with usage	Capacity adjusts automatically
3	Traffic decreases	ON_DEMAND	Auto scales down	Auto scales down	Charges decrease with usage	Capacity adjusts automatically
4	Create table with PROVISIONED mode	PROVISIONED	5	5	Pay fixed units	Table created with fixed capacity
5	Traffic increases beyond capacity	PROVISIONED	5	5	May throttle requests	Performance may degrade
6	Manually increase capacity	PROVISIONED	10	10	Pay fixed units	Capacity increased manually
7	Traffic normalizes	PROVISIONED	10	10	Pay fixed units	Capacity remains fixed until changed
8	End	-	-	-	-	Execution ends

💡 Execution ends after showing both modes handling traffic and billing differences.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 5	After Step 6	Final
Capacity Mode	Not set	ON_DEMAND	ON_DEMAND	PROVISIONED	PROVISIONED	PROVISIONED
Read Capacity Units (RCU)	N/A	Auto scales up	Auto scales down	5	10	10
Write Capacity Units (WCU)	N/A	Auto scales up	Auto scales down	5	10	10
Billing	N/A	Pay per request	Pay per request	Pay fixed units	Pay fixed units	Pay fixed units

Key Moments - 3 Insights

Why does on-demand mode not require setting read/write units?

Because on-demand mode automatically adjusts capacity based on traffic, as shown in execution_table rows 1-3 where capacity scales up and down without manual input.

What happens if traffic exceeds provisioned capacity?

Requests may be throttled causing performance issues, as seen in execution_table row 5 where fixed capacity is insufficient for increased traffic.

Does provisioned mode automatically reduce capacity when traffic decreases?

No, provisioned capacity stays fixed until manually changed, shown in rows 6-7 where capacity remains at 10 units despite traffic normalization.

Visual Quiz - 3 Questions

Look at the execution_table, what billing method is used in step 2 for on-demand mode?

A Pay fixed units

B Pay per request

C Free

D Subscription

💡 Hint

Check the 'Billing' column in execution_table row 2.

At which step does provisioned mode capacity get manually increased?

A Step 6

B Step 5

C Step 4

D Step 7

💡 Hint

Look at the 'Action' column describing capacity changes in execution_table.

If traffic decreases in on-demand mode, what happens to capacity according to variable_tracker?

A Capacity stays the same

B Capacity increases

C Capacity decreases automatically

D Capacity must be manually adjusted

💡 Hint

See 'Read Capacity Units (RCU)' and 'Write Capacity Units (WCU)' changes after Step 3 in variable_tracker.

Concept Snapshot

DynamoDB tables have two capacity modes:
- On-Demand: Auto scales read/write capacity, pay per request.
- Provisioned: Set fixed read/write units, pay fixed cost.
On-Demand suits unpredictable traffic.
Provisioned suits steady, predictable workloads.
Choose mode based on traffic pattern and cost control.

Full Transcript

This visual execution shows how DynamoDB table capacity modes work. You start by choosing either on-demand or provisioned mode. On-demand mode automatically adjusts capacity units based on traffic, charging you per request. Provisioned mode requires you to set fixed read and write capacity units, paying a fixed cost regardless of usage. If traffic exceeds provisioned capacity, requests may be throttled until you manually increase capacity. On-demand mode scales capacity up and down automatically as traffic changes. This helps you understand billing differences and performance impacts between the two modes.