Why Burst capacity in DynamoDB? - Purpose & Use Cases

The Big Idea

What if your database could magically handle sudden rushes of users without breaking a sweat?

The Scenario

Imagine you run a small online store. Most days, only a few customers visit your site, so your database handles a small number of requests. But suddenly, a big sale starts, and hundreds of customers rush in at once. Your database struggles to keep up.

The Problem

Without burst capacity, your database can only handle a fixed number of requests per second. When many users come at once, requests get delayed or dropped. This causes slow pages, lost orders, and unhappy customers. Manually adjusting capacity is slow and often too late.

The Solution

Burst capacity lets your database handle sudden spikes in traffic by temporarily allowing more requests than usual. It acts like a short-term boost, so your store stays fast and responsive during busy times without paying for extra capacity all the time.

Before vs After

✗ Before

ProvisionedCapacity = 100
// Fixed limit, no spikes allowed

✓ After

ProvisionedCapacity = 100
// Burst capacity enabled
// Handles sudden spikes smoothly

What It Enables

Burst capacity enables your database to smoothly handle sudden traffic spikes without downtime or slowdowns.

Real Life Example

During a holiday sale, thousands of shoppers visit your site at once. Burst capacity lets your database serve all requests quickly, preventing lost sales and keeping customers happy.

Key Takeaways

Burst capacity handles sudden traffic spikes automatically.

It prevents slowdowns and dropped requests during busy times.

It saves money by avoiding constant over-provisioning.

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