Auto-scaling configuration in DynamoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to specify the minimum capacity for auto-scaling.

DynamoDB

{
  "AutoScalingSettingsUpdate": {
    "MinimumUnits": [1]
  }
}

Drag options to blanks, or click blank then click option'

A"min"

B5

C-1

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using zero or negative numbers for MinimumUnits.

Using strings instead of numbers.

The MinimumUnits must be a positive integer specifying the minimum capacity units for auto-scaling.

2fill in blank

medium

Complete the code to set the target utilization percentage for auto-scaling.

DynamoDB

{
  "TargetTrackingScalingPolicyConfiguration": {
    "TargetValue": [1]
  }
}

Drag options to blanks, or click blank then click option'

A"high"

B150

C70

D-10

Attempts:

3 left

💡 Hint

Common Mistakes

Using values greater than 100 or negative values.

Using strings instead of numbers.

The TargetValue is a percentage (usually between 0 and 100) that defines the desired utilization for auto-scaling.

3fill in blank

hard

Fix the error in the code to correctly specify the scale-in cooldown period.

DynamoDB

{
  "ScaleInCooldown": [1]
}

Drag options to blanks, or click blank then click option'

A300

Bnull

C"300"

D-300

Attempts:

3 left

💡 Hint

Common Mistakes

Using string values instead of integers.

Using negative numbers or null.

The ScaleInCooldown must be a positive integer representing seconds. It cannot be a string or negative.

4fill in blank

hard

Fill both blanks to set the maximum and minimum capacity units for auto-scaling.

DynamoDB

{
  "AutoScalingSettingsUpdate": {
    "MaximumUnits": [1],
    "MinimumUnits": [2]
  }
}

Drag options to blanks, or click blank then click option'

A100

B10

C5

D200

Attempts:

3 left

💡 Hint

Common Mistakes

Setting MinimumUnits higher than MaximumUnits.

Using zero or negative numbers.

The MaximumUnits should be greater than the MinimumUnits. Here, 100 is max and 5 is min.

5fill in blank

hard

Fill all three blanks to configure the target tracking policy with cooldown periods and target value.

DynamoDB

{
  "TargetTrackingScalingPolicyConfiguration": {
    "TargetValue": [1],
    "ScaleInCooldown": [2],
    "ScaleOutCooldown": [3]
  }
}

Drag options to blanks, or click blank then click option'

A75

B60

C120

D30

Attempts:

3 left

💡 Hint

Common Mistakes

Using cooldown values as strings or negative numbers.

Setting TargetValue outside 0-100 range.

The TargetValue is 75%, ScaleInCooldown is 60 seconds, and ScaleOutCooldown is 120 seconds.

Practice

1. What is the main purpose of auto-scaling in DynamoDB?

easy

A. To encrypt data stored in the table

B. To manually set fixed capacity limits

C. To backup data at regular intervals

D. To automatically adjust read and write capacity based on traffic

Solution

1. Step 1: Understand auto-scaling function

   Auto-scaling automatically changes capacity to match traffic demands.

2. Step 2: Compare options

   Only To automatically adjust read and write capacity based on traffic describes automatic adjustment of capacity based on traffic.

3. Final Answer:

   To automatically adjust read and write capacity based on traffic -> Option D

4. Quick Check:

   Auto-scaling adjusts capacity automatically = A [OK]

Hint: Auto-scaling means automatic capacity adjustment [OK]

Common Mistakes:

• Confusing auto-scaling with manual capacity setting
• Thinking auto-scaling handles backups
• Mixing encryption with scaling

2. Which of the following is the correct way to specify the minimum capacity units in a DynamoDB auto-scaling policy JSON snippet?

easy

A. "MinCapacity": 5

B. "MinimumCapacityUnits": 5

C. "min_capacity": 5

D. "Min_Capacity": 5

Solution

1. Step 1: Recall DynamoDB auto-scaling JSON keys

   The correct key for minimum capacity is "MinCapacity" with camel case and no underscores.

2. Step 2: Check options

   Only "MinCapacity": 5 matches the exact key syntax "MinCapacity".

3. Final Answer:

   "MinCapacity": 5 -> Option A

4. Quick Check:

   Correct JSON key for minimum capacity = B [OK]

Hint: Use exact key names with correct casing in JSON [OK]

Common Mistakes:

• Using underscores instead of camel case
• Adding extra words like 'Units'
• Incorrect capitalization

3. Given this auto-scaling target tracking policy snippet:

{
  "TargetValue": 70.0,
  "ScaleInCooldown": 60,
  "ScaleOutCooldown": 60
}

What does the TargetValue represent?

medium

A. The maximum capacity units allowed

B. The cooldown time in seconds

C. The desired utilization percentage of capacity

D. The minimum capacity units allowed

Solution

1. Step 1: Understand TargetValue meaning

   TargetValue sets the target utilization percentage for capacity usage.

2. Step 2: Analyze options

   The desired utilization percentage of capacity correctly describes TargetValue as desired utilization percent (70%).

3. Final Answer:

   The desired utilization percentage of capacity -> Option C

4. Quick Check:

   TargetValue = utilization percent = C [OK]

Hint: TargetValue sets target usage percent, not capacity units [OK]

Common Mistakes:

• Confusing TargetValue with capacity limits
• Mixing cooldown times with TargetValue
• Thinking TargetValue is a fixed capacity number

4. You have this auto-scaling policy JSON snippet:

{
  "MinCapacity": 5,
  "MaxCapacity": 100,
  "TargetValue": 80.0,
  "ScaleInCooldown": 30,
  "ScaleOutCooldown": 30
}

But the policy is not working as expected. What is the likely error?

medium

A. MinCapacity is greater than MaxCapacity

B. Missing required field for resource ID

C. TargetValue should be between 0 and 1, not 80.0

D. Cooldown times are too short and cause rapid scaling

Solution

1. Step 1: Check capacity and cooldown values

   MinCapacity (5) is less than MaxCapacity (100), cooldowns are valid numbers.

2. Step 2: Identify missing required fields

   Auto-scaling policies require resource identifiers (like ResourceId) to apply the policy.

3. Step 3: Confirm TargetValue range

   TargetValue is a percentage and 80.0 is valid.

4. Final Answer:

   Missing required field for resource ID -> Option B

5. Quick Check:

   Missing resource ID causes policy failure = A [OK]

Hint: Check for all required fields, not just values [OK]

Common Mistakes:

• Assuming cooldown times cause failure
• Misreading TargetValue scale
• Ignoring missing resource identifiers

5. You want to configure auto-scaling for a DynamoDB table with unpredictable traffic spikes. Which combination of settings will best ensure smooth scaling without throttling or overspending?

{
  "MinCapacity": 10,
  "MaxCapacity": 200,
  "TargetValue": 70.0,
  "ScaleInCooldown": 120,
  "ScaleOutCooldown": 30
}

hard

A. Set a low MinCapacity, high MaxCapacity, fast ScaleOutCooldown, slow ScaleInCooldown

B. Set MinCapacity equal to MaxCapacity for fixed capacity

C. Set very fast ScaleInCooldown and ScaleOutCooldown both to 10 seconds

D. Set TargetValue to 100 to maximize usage

Solution

1. Step 1: Understand traffic spikes impact

   Unpredictable spikes need quick scaling out to avoid throttling and slower scaling in to avoid rapid capacity drops.

2. Step 2: Analyze given settings

   Low MinCapacity saves cost, high MaxCapacity allows growth, fast ScaleOutCooldown (30s) reacts quickly, slow ScaleInCooldown (120s) prevents rapid scale down.

3. Step 3: Evaluate other options

   Fixed capacity ignores spikes, very fast cooldowns cause thrashing, setting TargetValue to 100 risks overprovisioning.

4. Final Answer:

   Set a low MinCapacity, high MaxCapacity, fast ScaleOutCooldown, slow ScaleInCooldown -> Option A

5. Quick Check:

   Fast scale out + slow scale in = smooth scaling = D [OK]

Hint: Fast scale out, slow scale in for spike handling [OK]

Common Mistakes:

• Setting fixed capacity ignoring spikes
• Using equal cooldowns causing rapid scaling
• Setting TargetValue too high causing overspending