Scheduled scaling in AWS - Step-by-Step Execution

Process Flow - Scheduled scaling

Define schedule

↓

Set desired capacity

↓

AWS Auto Scaling service waits

↓

Scheduled time reached?

No→Wait

Yes↓

Change capacity to desired

↓

Maintain capacity until next schedule

Scheduled scaling sets the number of servers at specific times automatically.

Execution Sample

AWS

ScheduledAction:
  Schedule: 'cron(0 8 * * ? *)'
  DesiredCapacity: 5
  MinSize: 2
  MaxSize: 10

This sets the server count to 5 every day at 8 AM.

Process Table

Step	Time	Scheduled Action Triggered?	Desired Capacity Set	Auto Scaling Group Capacity
1	7:59 AM	No	N/A	3 (previous)
2	8:00 AM	Yes	5	5 (scaled up)
3	12:00 PM	No	N/A	5 (unchanged)
4	8:00 PM	No	N/A	5 (unchanged)
5	Next day 8:00 AM	Yes	5	5 (maintained)

💡 Scheduled scaling triggers only at defined times; capacity stays until next trigger.

Status Tracker

Variable	Start	After Step 2	After Step 3	After Step 5
Auto Scaling Group Capacity	3	5	5	5
Desired Capacity	N/A	5	5	5

Key Moments - 2 Insights

Why doesn't the capacity change at 12:00 PM even though time has passed?

Because scheduled scaling only triggers at the exact scheduled time (8:00 AM), not continuously. See execution_table step 3.

What happens if the desired capacity is set lower than the current capacity?

Auto Scaling will reduce the number of servers to the desired capacity at the scheduled time, ensuring resources match the schedule.

Visual Quiz - 3 Questions

Look at the execution table, what is the Auto Scaling Group capacity at 7:59 AM?

A 0

B 3

C 5

D 10

💡 Hint

Check the first row under 'Auto Scaling Group Capacity' in execution_table.

At which step does the scheduled scaling action trigger?

A Step 3

B Step 1

C Step 2

D Step 4

💡 Hint

Look for 'Scheduled Action Triggered?' column in execution_table.

If the desired capacity was changed to 7 at 8:00 AM, what would happen at Step 2?

A Capacity changes to 7

B Capacity changes to 5

C Capacity stays at 3

D Capacity changes to 10

💡 Hint

Desired Capacity column in variable_tracker shows what capacity is set at scheduled time.

Concept Snapshot

Scheduled scaling lets you set server counts at specific times.
You define a schedule and desired capacity.
At the scheduled time, capacity changes automatically.
Capacity stays until next scheduled change.
Useful for predictable traffic patterns.

Full Transcript

Scheduled scaling in AWS Auto Scaling lets you automatically adjust the number of servers at specific times you choose. You define a schedule using cron or rate expressions and set the desired number of servers. When the scheduled time arrives, AWS changes the capacity to your desired number. Between scheduled times, the capacity remains steady. This helps save costs and ensures enough servers during busy times. For example, setting desired capacity to 5 at 8 AM means every day at 8 AM, the system scales to 5 servers. The execution table shows capacity before and after scheduled triggers. Capacity only changes at scheduled times, not continuously. If you change the desired capacity in the schedule, the system adjusts accordingly at the next trigger.