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The 128-hour Gap⏰: Where Your Aws Budget Is Leaking

Non-prod Auto Scaling Groups running at full capacity 24/7 waste 70% of costs. Here's how to add scheduled scaling with 5 lines of Terraform and reclaim those hours.

Reality check: Your development and QA environments run 24/7, but your team works 9-5, Monday-Friday.

The math:

Hours per week: 168 total  
Developer hours: 40-50 (weekdays)  
Wasted hours: 118-128 (nights + weekends)  
  
Your dev environment is idle 70% of the time.  
But you're paying 100% of the cost.

Typical dev environment:

3 EC2 instances (t3.large) = $225/month
Needed hours: 40/week
Actual usage: 70% waste
You could pay: $70/month instead

Let me show you how to add scheduled scaling with literally 5 lines of Terraform and slash your non-prod costs by 65%.

???? The Always-On Tax

Most dev/staging/QA environments look like this:

Auto Scaling Group config:

Min: 3 instances  
Max: 6 instances  
Desired: 3 instances  
Schedule: None (runs 24/7)

Cost breakdown:

3 × t3.large instances  
  - $0.0832/hour × 3 × 730 hours = $182/month  
  - EBS volumes: $24/month  
  - Load balancer: $16/month  
Total: $222/month  
Annual: $2,664  
  
Actual needed hours: 50 hours/week = 217 hours/month  
Waste: 513 hours/month (70% waste!)  
Wasted money: $155/month = $1,860/year

???? The Solution: Scheduled Actions

Auto Scaling Groups support scheduled actions - change capacity on a schedule.

Strategy:

Business hours (8 AM - 6 PM weekdays): Full capacity
Nights and weekends: Scale to zero (or minimal)

Implementation: 5 lines of Terraform per schedule.

????️ Terraform Implementation

Basic Weekday Schedule

# asg-scheduled-scaling.tf  
  
# Scale UP for business hours (8 AM Monday-Friday)  
resource "aws_autoscaling_schedule" "scale_up_weekday" {  
  scheduled_action_name  = "scale-up-weekday"  
  min_size               = 3  
  max_size               = 6  
  desired_capacity       = 3  
  recurrence             = "0 8 * * 1-5"  # 8 AM Mon-Fri (UTC)  
  autoscaling_group_name = aws_autoscaling_group.dev.name  
}  
  
# Scale DOWN for nights (6 PM Monday-Friday)  
resource "aws_autoscaling_schedule" "scale_down_weekday" {  
  scheduled_action_name  = "scale-down-weekday"  
  min_size               = 1  
  max_size               = 2  
  desired_capacity       = 1  
  recurrence             = "0 18 * * 1-5"  # 6 PM Mon-Fri (UTC)  
  autoscaling_group_name = aws_autoscaling_group.dev.name  
}  
  
# Scale DOWN for weekends (Friday night)  
resource "aws_autoscaling_schedule" "scale_down_weekend" {  
  scheduled_action_name  = "scale-down-weekend"  
  min_size               = 1  
  max_size               = 2  
  desired_capacity       = 1  
  recurrence             = "0 18 * * 5"  # 6 PM Friday (UTC)  
  autoscaling_group_name = aws_autoscaling_group.dev.name  
}  
  
# Scale UP Monday morning  
resource "aws_autoscaling_schedule" "scale_up_monday" {  
  scheduled_action_name  = "scale-up-monday"  
  min_size               = 3  
  max_size               = 6  
  desired_capacity       = 3  
  recurrence             = "0 8 * * 1"  # 8 AM Monday (UTC)  
  autoscaling_group_name = aws_autoscaling_group.dev.name  
}

That's it! 4 scheduled actions, 20 lines of code, done. ✅

Production-Ready Module

# modules/asg-scheduled-scaling/main.tf  
  
variable "asg_name" {  
  description = "Auto Scaling Group name"  
  type        = string  
}  
  
variable "business_hours" {  
  description = "Business hours configuration"  
  type = object({  
    min_size         = number  
    max_size         = number  
    desired_capacity = number  
    start_hour       = number  # 8 = 8 AM  
    end_hour         = number  # 18 = 6 PM  
  })  
  default = {  
    min_size         = 3  
    max_size         = 6  
    desired_capacity = 3  
    start_hour       = 8  
    end_hour         = 18  
  }  
}  
  
variable "off_hours" {  
  description = "Off-hours configuration"  
  type = object({  
    min_size         = number  
    max_size         = number  
    desired_capacity = number  
  })  
  default = {  
    min_size         = 1  
    max_size         = 2  
    desired_capacity = 1  
  }  
}  
  
variable "timezone_offset" {  
  description = "Hours offset from UTC (e.g., -5 for EST)"  
  type        = number  
  default     = 0  
}  
  
locals {  
  # Adjust hours for timezone  
  start_hour_utc = (var.business_hours.start_hour - var.timezone_offset) % 24  
  end_hour_utc   = (var.business_hours.end_hour - var.timezone_offset) % 24  
}  
  
# Scale up for business hours (weekdays)  
resource "aws_autoscaling_schedule" "scale_up" {  
  scheduled_action_name  = "${var.asg_name}-scale-up-weekday"  
  min_size               = var.business_hours.min_size  
  max_size               = var.business_hours.max_size  
  desired_capacity       = var.business_hours.desired_capacity  
  recurrence             = "${local.start_hour_utc} * * 1-5"  
  autoscaling_group_name = var.asg_name  
}  
  
# Scale down for nights/weekends  
resource "aws_autoscaling_schedule" "scale_down" {  
  scheduled_action_name  = "${var.asg_name}-scale-down-weekday"  
  min_size               = var.off_hours.min_size  
  max_size               = var.off_hours.max_size  
  desired_capacity       = var.off_hours.desired_capacity  
  recurrence             = "${local.end_hour_utc} * * 1-5"  
  autoscaling_group_name = var.asg_name  
}  
  
output "schedules_created" {  
  value = {  
    scale_up   = aws_autoscaling_schedule.scale_up.scheduled_action_name  
    scale_down = aws_autoscaling_schedule.scale_down.scheduled_action_name  
  }  
}

Usage

# main.tf  
  
# Dev environment - keep 1 instance off-hours  
module "dev_scaling" {  
  source = "./modules/asg-scheduled-scaling"  
  
  asg_name        = aws_autoscaling_group.dev.name  
  timezone_offset = -5  # EST  
  
  business_hours = {  
    min_size         = 2  
    max_size         = 5  
    desired_capacity = 2  
    start_hour       = 8   # 8 AM EST  
    end_hour         = 18  # 6 PM EST  
  }  
  
  off_hours = {  
    min_size         = 1  
    max_size         = 2  
    desired_capacity = 1  # Keep 1 instance for CI/CD  
  }  
}  
  
# QA environment - keep 1 instance off-hours  
module "qa_scaling" {  
  source = "./modules/asg-scheduled-scaling"  
  
  asg_name        = aws_autoscaling_group.qa.name  
  timezone_offset = -5  
  
  business_hours = {  
    min_size         = 3  
    max_size         = 6  
    desired_capacity = 3  
    start_hour       = 7   # 7 AM EST (earlier for pre-work testing)  
    end_hour         = 20  # 8 PM EST (later for evening testing)  
  }  
  
  off_hours = {  
    min_size         = 1   # Keep 1 for overnight tests  
    max_size         = 2  
    desired_capacity = 1  
  }  
}  
  
# Staging - keep 1 instance on weekends  
module "staging_scaling" {  
  source = "./modules/asg-scheduled-scaling"  
  
  asg_name        = aws_autoscaling_group.staging.name  
  timezone_offset = -5  
  
  business_hours = {  
    min_size         = 2  
    max_size         = 4  
    desired_capacity = 2  
    start_hour       = 6   # 6 AM Monday  
    end_hour         = 22  # 10 PM Friday  
  }  
  
  off_hours = {  
    min_size         = 1  
    max_size         = 2  
    desired_capacity = 1  # Keep 1 on weekends  
  }  
}

???? Cost Savings Breakdown

Dev Environment (Keep 1 Instance Off-Hours)

Before:

3 × t3.large running 24/7  
  - 3 × $0.0832/hour × 730 hours = $182/month  
  - Annual: $2,184

After (3 instances business hours, 1 instance off-hours):

Business hours (50 hrs/week = 217 hrs/month): 3 instances  
Off-hours (118 hrs/week = 513 hrs/month): 1 instance  
  
3 × $0.0832 × 217 + 1 × $0.0832 × 513  
= $54 + $43 = $97/month  
Annual: $1,164  
  
Savings: $85/month = $1,020/year (47% reduction!) ????

QA Environment (1 Instance Off-Hours)

Before:

4 × t3.xlarge running 24/7 = $485/month

After:

Business hours (60 hrs/week): 4 instances  
Off-hours (108 hrs/week): 1 instance  
  
4 × $0.1664/hour × 260 hrs + 1 × $0.1664/hour × 470 hrs  
= $173 + $78 = $251/month  
  
Savings: $234/month = $2,808/year (48% reduction!)

Typical Organization (5 Non-Prod Environments)

2 Dev + 2 QA + 1 Staging = 5 environments  
Average cost before: $300/month each = $1,500/month  
  
After scheduled scaling:  
  - Dev (2): $97/month each = $194  
  - QA (2): $150/month each = $300  
  - Staging: $120/month  
  
Total after: $614/month  
Savings: $886/month = $10,632/year ????

???? Pro Tips

1. Account for Timezone

Scheduled actions use UTC time. Convert from your timezone:

# EST (UTC-5)  
start_hour = 8   # 8 AM EST  
utc_hour = 8 + 5 = 13  # 1 PM UTC  
  
recurrence = "0 13 * * 1-5"  # Use UTC hour in cron

Or use the module which handles conversion automatically!

2. Keep Minimal Capacity for Tests

Don't scale to absolute zero if you have:

Overnight CI/CD jobs
Automated testing suites
Health checks that need to pass

off_hours = {  
  min_size         = 1  # Keep 1 instance  
  desired_capacity = 1  
}

3. Stagger Scale-Up Times

Avoid resource contention by staggering start times:

# Dev starts at 8 AM  
recurrence = "0 8 * * 1-5"  
  
# QA starts at 8:15 AM  
recurrence = "15 8 * * 1-5"  
  
# Staging starts at 8:30 AM  
recurrence = "30 8 * * 1-5"

4. Monitor Scale Events

Set up CloudWatch alarms:

resource "aws_cloudwatch_metric_alarm" "scale_up_success" {  
  alarm_name          = "dev-scale-up-verification"  
  comparison_operator = "LessThanThreshold"  
  evaluation_periods  = 1  
  metric_name         = "GroupDesiredCapacity"  
  namespace           = "AWS/AutoScaling"  
  period              = 300  
  statistic           = "Average"  
  threshold           = 3  
  alarm_description   = "Dev ASG failed to scale up at 8 AM"  
  
  dimensions = {  
    AutoScalingGroupName = aws_autoscaling_group.dev.name  
  }  
}

5. Add Holidays

Extend weekend shutdown for holidays:

# Thanksgiving week shutdown  
resource "aws_autoscaling_schedule" "thanksgiving" {  
  scheduled_action_name  = "thanksgiving-shutdown"  
  min_size               = 0  
  max_size               = 1  
  desired_capacity       = 0  
  start_time             = "2024-11-27T00:00:00Z"  
  end_time               = "2024-12-02T08:00:00Z"  
  autoscaling_group_name = aws_autoscaling_group.dev.name  
}

⚡ Quick Start

# 1. Add scheduled actions to existing ASG  
terraform apply  
  
# 2. Verify schedules created  
aws autoscaling describe-scheduled-actions \  
  --auto-scaling-group-name dev-asg  
  
# 3. Test scale-down manually (optional)  
aws autoscaling set-desired-capacity \  
  --auto-scaling-group-name dev-asg \  
  --desired-capacity 0  
  
# 4. Wait and verify instances terminate  
aws ec2 describe-instances \  
  --filters "Name=tag:aws:autoscaling:groupName,Values=dev-asg" \  
  --query 'Reservations[].Instances[].State.Name'  
  
# 5. Watch your bill drop next month ????

⚠️ Common Gotchas

1. Cron Syntax is UTC, Not Local Time

# WRONG - This is NOT 8 AM EST  
recurrence = "0 8 * * 1-5"  # This is 8 AM UTC = 3 AM EST  
  
# RIGHT - 8 AM EST = 1 PM UTC  
recurrence = "0 13 * * 1-5"

2. Min/Max/Desired Must Be Consistent

# WRONG - Desired > Max  
min_size         = 0  
max_size         = 2  
desired_capacity = 3  # Error!  
  
# RIGHT  
min_size         = 0  
max_size         = 3  
desired_capacity = 3

3. Conflicting Schedules

# WRONG - Both run at 8 AM Monday  
recurrence = "0 8 * * 1-5"  # Weekday scale up  
recurrence = "0 8 * * 1"    # Monday scale up (conflicts!)  
  
# RIGHT - Monday schedule is redundant, remove it  
recurrence = "0 8 * * 1-5"  # Covers Monday too

4. Stateful Applications

If your instances store state (databases, sessions):

Don't scale to 0
Use lifecycle hooks to drain connections
Or better: make instances stateless!

???? Decision Matrix

Environment	Recommended Strategy	Expected Savings
Dev	Keep 1 instance off-hours	40-50%
QA	Keep 1 instance off-hours	50-60%
Staging	Keep 1 instance on weekends	30-40%
Demo	Scale to 1 except during demos	60-70%
Training	Keep 1 instance, scale up for sessions	70-80%

???? Real-World Example

Company: SaaS startup with 3 non-prod environments

Before scheduled scaling:

Dev:     3 × t3.large × 24/7    = $182/month  
QA:      4 × t3.xlarge × 24/7   = $485/month  
Staging: 2 × t3.large × 24/7    = $121/month  
  
Total: $788/month  
Annual: $9,456

After scheduled scaling:

Dev:     3 inst. business hours, 1 off-hours = $97/month  
QA:      60 hrs/week, 1 inst off-hours       = $251/month  
Staging: Weekdays 2 inst., weekends 1 inst.  = $120/month  
  
Total: $468/month  
Annual: $5,616  
  
Savings: $320/month = $3,840/year (41% reduction!)

Implementation time: 1 hour

Lines of Terraform: ~40

Ongoing maintenance: Zero

???? Summary

The Problem:

Non-prod environments run 24/7
Developers work 40-50 hours/week
70% of capacity is wasted
Costs accumulate unnecessarily

The Solution:

Auto Scaling scheduled actions
5 lines of Terraform per schedule
Scale down nights and weekends
Zero application changes needed

The Result:

Typical savings: 40-60% on non-prod
One-time setup, runs forever
No operational overhead
Works with existing ASGs
Keeps minimal capacity for CI/CD

Stop running dev environments at full capacity 24/7 when your team works 9-5. Add scheduled scaling and reclaim those wasted hours. ⏰

Implemented scheduled scaling? How much did you save? Share in the comments! ????

Follow for more AWS cost optimization with Terraform! ⚡

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