Burst capacity in DynamoDB - Step-by-Step Execution

Concept Flow - Burst capacity

Start with baseline capacity

↓

Traffic spikes occur?

No→Use baseline capacity

Yes↓

Use burst capacity credits

↓

Credits decrease

↓

Credits exhausted?

No→Continue burst

Yes↓

Throttle requests or wait for credits to replenish

Burst capacity lets your database handle sudden traffic spikes by using saved credits above baseline capacity, until credits run out.

Execution Sample

DynamoDB

BaselineCapacity = 100
Credits = 200
RequestRate = [50, 120, 180, 90, 130]

for rate in RequestRate:
  if rate > BaselineCapacity:
    Use credits
  else:
    Use baseline

This simulates how burst capacity credits are used when request rate exceeds baseline capacity.

Execution Table

Step	Request Rate	Baseline Capacity	Credits Before	Credits Used	Credits After	Capacity Used	Throttle?
1	50	100	200	0	200	50 (baseline)	No
2	120	100	200	20	180	100 (baseline) + 20 (credits)	No
3	180	100	180	80	100	100 (baseline) + 80 (credits)	No
4	90	100	100	0	100	90 (baseline)	No
5	130	100	100	30	70	100 (baseline) + 30 (credits)	No

💡 Credits remain after last request, no throttling needed.

Variable Tracker

Variable	Start	After 1	After 2	After 3	After 4	After 5
Credits	200	200	180	100	100	70

Key Moments - 2 Insights

Why do credits only decrease when request rate exceeds baseline capacity?

Because baseline capacity handles normal traffic without using credits, as shown in execution_table rows 1 and 4 where credits stay the same.

What happens when credits run out?

Requests exceeding baseline capacity cannot be served immediately and may be throttled or delayed, but in this example credits remain positive, so no throttling occurs.

Visual Quiz - 3 Questions

Look at the execution table, how many credits are used at step 3?

A 180

B 80

C 100

D 0

💡 Hint

Check the 'Credits Used' column at step 3 in the execution_table.

At which step does the request rate NOT use any credits?

A Step 4

B Step 2

C Step 5

D Step 3

💡 Hint

Look for rows where 'Credits Used' is 0 in the execution_table.

If the baseline capacity was increased to 150, what would happen at step 2?

A Credits would increase

B Credits would be used as before

C No credits would be used because request rate is below baseline

D Request would be throttled

💡 Hint

Compare request rate and baseline capacity at step 2 in the execution_table and consider the new baseline.

Concept Snapshot

Burst capacity lets DynamoDB handle sudden traffic spikes by using saved credits above baseline capacity.
Credits are consumed only when request rate exceeds baseline.
When credits run out, requests may be throttled.
Credits replenish over time during low traffic.
This helps maintain performance without over-provisioning.

Full Transcript

Burst capacity in DynamoDB allows the database to handle sudden increases in traffic by using saved capacity credits. The baseline capacity is the normal throughput the database can handle without extra cost. When requests exceed this baseline, burst credits are used to serve the extra load. Credits decrease as they are used and replenish when traffic is low. If credits run out, requests may be throttled or delayed until credits are available again. This mechanism helps maintain smooth performance during traffic spikes without needing to permanently increase capacity.

Practice

1. What is the main purpose of burst capacity in DynamoDB?

easy

A. To backup data automatically

B. To permanently increase table throughput

C. To handle sudden spikes in traffic smoothly

D. To reduce storage costs

Solution

1. Step 1: Understand burst capacity concept

   Burst capacity allows DynamoDB to use unused capacity from earlier low traffic periods.

2. Step 2: Identify its main use

   This helps handle sudden traffic spikes smoothly without extra setup.

3. Final Answer:

   To handle sudden spikes in traffic smoothly -> Option C

4. Quick Check:

   Burst capacity = handle spikes [OK]

Hint: Burst capacity smooths sudden traffic spikes [OK]

Common Mistakes:

• Thinking burst capacity permanently increases throughput
• Confusing burst capacity with backup or storage features
• Assuming manual code is needed to use burst capacity

2. Which of the following statements about DynamoDB burst capacity is syntactically correct?

easy

A. BurstCapacity: enabled

B. ProvisionedThroughput: { ReadCapacityUnits: 5, WriteCapacityUnits: 5 }

C. EnableBurstCapacity = true

D. SetBurstCapacity(5)

Solution

1. Step 1: Check valid DynamoDB syntax

   ProvisionedThroughput with ReadCapacityUnits and WriteCapacityUnits is valid for table setup.

2. Step 2: Identify invalid options

   Options B, C, and D are not valid DynamoDB syntax or parameters.

3. Final Answer:

   <code>ProvisionedThroughput: { ReadCapacityUnits: 5, WriteCapacityUnits: 5 }</code> -> Option B

4. Quick Check:

   Valid syntax = ProvisionedThroughput: { ReadCapacityUnits: 5, WriteCapacityUnits: 5 } [OK]

Hint: Only ProvisionedThroughput syntax is valid here [OK]

Common Mistakes:

• Assuming burst capacity needs explicit enabling syntax
• Using incorrect parameter names
• Confusing configuration with method calls

3. Consider a DynamoDB table with provisioned read capacity of 10 units. The table has been idle for a while, accumulating unused capacity. Suddenly, a spike causes 15 read requests per second. What will happen?

medium

A. The table will reject all requests during the spike

B. The table will throttle all requests above 10 units immediately

C. The table will automatically increase provisioned capacity to 15 units

D. The table will use burst capacity to handle some requests above 10 units

Solution

1. Step 1: Understand idle capacity accumulation

   Unused capacity from idle periods accumulates as burst capacity credits.

2. Step 2: Apply burst capacity during spike

   When requests exceed provisioned units, DynamoDB uses burst capacity to handle some extra requests smoothly.

3. Final Answer:

   The table will use burst capacity to handle some requests above 10 units -> Option D

4. Quick Check:

   Burst capacity handles spikes above provisioned [OK]

Hint: Burst capacity covers temporary spikes above provisioned [OK]

Common Mistakes:

• Thinking DynamoDB instantly throttles above provisioned units
• Assuming automatic permanent capacity increase
• Believing all requests are rejected during spikes

4. You notice your DynamoDB table is throttling requests during a traffic spike, even though it was idle before. What is the most likely cause?

medium

A. Burst capacity credits were already used up before the spike

B. Provisioned throughput is set too high

C. Burst capacity must be manually enabled

D. The table is in on-demand mode

Solution

1. Step 1: Analyze burst capacity usage

   Burst capacity depends on unused capacity credits accumulated during idle times.

2. Step 2: Reason about throttling cause

   If credits are used up, the table cannot handle spikes beyond provisioned throughput, causing throttling.

3. Final Answer:

   Burst capacity credits were already used up before the spike -> Option A

4. Quick Check:

   Throttling = no burst credits left [OK]

Hint: No burst credits means throttling during spikes [OK]

Common Mistakes:

• Thinking burst capacity needs manual enabling
• Assuming high provisioned throughput causes throttling
• Confusing on-demand mode with provisioned burst capacity

5. A DynamoDB table has a provisioned write capacity of 20 units. It was idle for 10 minutes, then suddenly receives 50 write requests per second for 1 minute. How does burst capacity affect this scenario?

hard

A. Burst capacity allows some requests above 20 units to succeed temporarily

B. Burst capacity automatically increases provisioned capacity to 50 units

C. Burst capacity allows all 50 requests to succeed without throttling

D. Burst capacity does not apply to write requests

Solution

1. Step 1: Understand burst capacity accumulation

   Idle time accumulates unused write capacity credits that can be used in bursts.

2. Step 2: Apply burst capacity during spike

   During the spike, burst capacity allows handling some requests above provisioned 20 units temporarily, but not all 50.

3. Final Answer:

   Burst capacity allows some requests above 20 units to succeed temporarily -> Option A

4. Quick Check:

   Burst capacity = temporary extra writes above provisioned [OK]

Hint: Burst capacity helps some writes above provisioned temporarily [OK]

Common Mistakes:

• Assuming burst capacity handles all spike requests fully
• Thinking burst capacity increases provisioned throughput permanently
• Believing burst capacity applies only to reads