Scheduled scaling in AWS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is scheduled scaling in cloud infrastructure?

Scheduled scaling is a way to automatically adjust the number of resources, like servers, at specific times. It helps prepare for expected changes in demand, like more users during the day and fewer at night.

beginner

Why use scheduled scaling instead of manual scaling?

Scheduled scaling saves time and reduces errors by automatically changing resource levels at set times. This ensures resources are ready when needed without waiting for someone to act.

beginner

In AWS, which service commonly uses scheduled scaling?

AWS Auto Scaling groups use scheduled scaling to increase or decrease the number of EC2 instances based on a schedule you set.

beginner

What is a real-life example of scheduled scaling?

Imagine a coffee shop that knows more customers come in the morning. They schedule more staff to work then and fewer in the afternoon. Scheduled scaling does the same for cloud resources.

beginner

What is a key benefit of scheduled scaling for cost management?

Scheduled scaling helps reduce costs by lowering resources when demand is low, so you don’t pay for unused capacity.

What does scheduled scaling do in cloud services?

A Backs up data regularly

B Automatically adjusts resources at set times

C Monitors security threats

D Manually adds resources when requested

Scheduled scaling automatically changes resource levels based on a schedule.

Which AWS service uses scheduled scaling to manage server numbers?

A AWS Lambda

B Amazon S3

C Auto Scaling groups

D Amazon RDS

Auto Scaling groups adjust EC2 instance counts using scheduled scaling.

What is a main advantage of scheduled scaling?

A Prepares resources before demand spikes

B Increases manual work

C Deletes unused data

D Encrypts all data

Scheduled scaling prepares resources ahead of expected demand increases.

Scheduled scaling helps reduce costs by:

A Lowering resources when demand is low

B Increasing resources randomly

C Running all resources 24/7

D Backing up data frequently

It lowers resources during low demand to avoid paying for unused capacity.

Which scenario best fits scheduled scaling?

A Scaling resources only when a problem occurs

B Scaling resources randomly

C Never changing resource levels

D Scaling resources based on a fixed daily schedule

Scheduled scaling adjusts resources based on a planned schedule.

Explain what scheduled scaling is and why it is useful in cloud computing.

Think about how you might prepare for busy and quiet times in a store.

Describe how AWS Auto Scaling groups use scheduled scaling to manage EC2 instances.

Focus on how AWS changes server numbers automatically at planned times.

Practice

1. What is the main purpose of scheduled scaling in AWS?

easy

A. To automatically adjust resources at specific times

B. To manually increase server capacity when needed

C. To monitor security threats in real-time

D. To backup data at scheduled intervals

Solution

1. Step 1: Understand scheduled scaling concept

   Scheduled scaling is designed to change resource capacity automatically based on a set schedule.

2. Step 2: Compare options with the concept

   Only To automatically adjust resources at specific times describes automatic adjustment at specific times, matching scheduled scaling.

3. Final Answer:

   To automatically adjust resources at specific times -> Option A

4. Quick Check:

   Scheduled scaling = automatic timed resource adjustment [OK]

Hint: Scheduled scaling means automatic resource changes on a timer [OK]

Common Mistakes:

• Confusing scheduled scaling with manual scaling
• Thinking it handles security or backups
• Assuming it reacts only to traffic, not time

2. Which of the following is a valid cron expression for scheduled scaling in AWS?

easy

A. cron(0 0 0 0 ? *)

B. cron(60 24 * * ? *)

C. cron(* * * * *)

D. cron(0 12 * * ? *)

Solution

1. Step 1: Review cron expression format in AWS

   AWS cron expressions have six fields: minutes, hours, day-of-month, month, day-of-week, year.

2. Step 2: Validate each option

   cron(0 12 * * ? *) is valid: minute=0, hour=12, day-of-month=*, month=*, day-of-week=?, year=*. cron(0 0 0 0 ? *) has invalid zero day-of-month and month values. cron(60 24 * * ? *) has invalid 60 minutes and 24 hours. cron(* * * * *) has only five fields, missing year.

3. Final Answer:

   cron(0 12 * * ? *) -> Option D

4. Quick Check:

   Valid AWS cron = 6 fields, correct ranges [OK]

Hint: AWS cron needs 6 fields with valid ranges [OK]

Common Mistakes:

• Using 5-field cron instead of 6-field
• Setting minutes or hours out of range
• Confusing day-of-week and day-of-month

3. Given this scheduled scaling configuration snippet:

{"ScheduledActionName": "ScaleUpMorning", "StartTime": "2024-07-01T08:00:00Z", "DesiredCapacity": 5}

What will happen at 8 AM UTC on July 1, 2024?

medium

A. The resource capacity will be set to 5

B. The resource capacity will decrease to 0

C. The scaling action will be ignored due to missing EndTime

D. The resource capacity will remain unchanged

Solution

1. Step 1: Understand the scheduled action parameters

   The action named "ScaleUpMorning" is set to start at 8 AM UTC on July 1, 2024, with DesiredCapacity 5.

2. Step 2: Interpret the effect of StartTime and DesiredCapacity

   At the StartTime, the capacity will be set to 5. EndTime is optional and does not block the action.

3. Final Answer:

   The resource capacity will be set to 5 -> Option A

4. Quick Check:

   StartTime triggers capacity change to DesiredCapacity [OK]

Hint: StartTime sets capacity; EndTime is optional [OK]

Common Mistakes:

• Thinking EndTime is required to trigger scaling
• Assuming capacity decreases without explicit setting
• Ignoring the StartTime effect

4. You created a scheduled scaling action with this cron expression:
cron(0 25 * * ? *)
Why does the scaling not trigger as expected?

medium

A. The day-of-week field is missing

B. The minute value 0 is invalid

C. The hour value 25 is invalid in cron expressions

D. The cron expression needs only 5 fields

Solution

1. Step 1: Check the hour field in the cron expression

   The hour field is set to 25, but valid hour values are 0 to 23.

2. Step 2: Understand cron validation rules in AWS

   AWS rejects cron expressions with invalid field values, so the scaling action won't trigger.

3. Final Answer:

   The hour value 25 is invalid in cron expressions -> Option C

4. Quick Check:

   Hour must be 0-23 in AWS cron [OK]

Hint: Check cron field ranges; hours max 23 [OK]

Common Mistakes:

• Assuming minute 0 is invalid
• Thinking day-of-week is mandatory
• Using 5 fields instead of 6

5. You want to reduce your AWS Auto Scaling group capacity to 2 instances every night at 11 PM UTC and increase it to 10 instances every weekday morning at 7 AM UTC. Which setup correctly uses scheduled scaling to achieve this?

hard

A. Create one scheduled action with cron(0 23,7 * * ? *) setting DesiredCapacity=2 and DesiredCapacity=10

B. Create two scheduled actions: one with cron(0 23 * * ? *) setting DesiredCapacity=2, another with cron(0 7 ? * MON-FRI *) setting DesiredCapacity=10

C. Create two scheduled actions: one with rate(1 day) setting DesiredCapacity=2, another with rate(1 hour) setting DesiredCapacity=10

D. Create one scheduled action with cron(0 7 * * ? *) setting DesiredCapacity=10 only

Solution

1. Step 1: Understand the scheduling requirements

   Capacity should be 2 at 11 PM daily and 10 at 7 AM on weekdays only.

2. Step 2: Match cron expressions to requirements

   cron(0 23 * * ? *) runs daily at 11 PM; cron(0 7 ? * MON-FRI *) runs at 7 AM Monday to Friday. Two separate scheduled actions are needed with correct DesiredCapacity values.

3. Final Answer:

   Create two scheduled actions: one with cron(0 23 * * ? *) setting DesiredCapacity=2, another with cron(0 7 ? * MON-FRI *) setting DesiredCapacity=10 -> Option B

4. Quick Check:

   Separate cron for each time and capacity [OK]

Hint: Use separate scheduled actions with correct cron and capacity [OK]

Common Mistakes:

• Trying to set two capacities in one scheduled action
• Using rate expressions instead of cron for weekdays
• Missing weekday restriction for morning scale-up