Spot Instances for cost savings in AWS - Step-by-Step Execution

Process Flow - Spot Instances for cost savings

Request Spot Instance

↓

AWS checks capacity & price

↓

Capacity OK?

↓

Instance Launch

↓

Instance Runs

↓

Spot Price Changes?

↓

Price <= Bid?

↓

Keep Running

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Save Costs vs On-Demand

This flow shows how AWS processes a Spot Instance request, launches it if capacity and price conditions are met, and may terminate it if the spot price rises above your bid.

Execution Sample

AWS

Request Spot Instance with max price $0.05
AWS checks capacity and current spot price
If capacity available and price <= $0.05, launch instance
Instance runs until spot price > $0.05 or terminated
Save costs compared to on-demand instance

This example requests a Spot Instance with a max price and shows how AWS decides to launch or terminate it based on capacity and price.

Process Table

Step	Action	Capacity Available?	Spot Price ($)	Bid Price ($)	Result	Cost Saving
1	Request Spot Instance	N/A	N/A	0.05	Request sent	N/A
2	AWS checks capacity and price	Yes	0.04	0.05	Instance launched	Yes
3	Instance runs	Yes	0.04	0.05	Running	Yes
4	Spot price rises	Yes	0.06	0.05	Instance terminated	Yes
5	Request retry or fallback	Depends	Varies	0.05	Wait or fail	N/A
6	End	N/A	N/A	N/A	Process ends	Cost saved compared to on-demand

💡 Execution stops when instance is terminated due to spot price exceeding bid or capacity unavailable.

Status Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
Capacity Available	N/A	Yes	Yes	Yes	N/A
Spot Price ($)	N/A	0.04	0.04	0.06	N/A
Bid Price ($)	0.05	0.05	0.05	0.05	N/A
Instance State	Requested	Launched	Running	Terminated	N/A
Cost Saving	N/A	Yes	Yes	Yes	Yes

Key Moments - 3 Insights

Why might my Spot Instance request not launch immediately?

If capacity is not available or the current spot price is higher than your bid price, AWS will not launch the instance immediately (see execution_table step 2).

What causes my running Spot Instance to be terminated?

If the spot price rises above your bid price while your instance is running, AWS will terminate it to reclaim capacity (see execution_table step 4).

Do I always save money using Spot Instances?

Yes, Spot Instances cost less than on-demand, but they can be interrupted, so savings come with the risk of termination (see execution_table exit_note).

Visual Quiz - 3 Questions

Look at the execution_table at step 2, what conditions must be true for the instance to launch?

A Capacity available and spot price less than or equal to bid price

B Capacity unavailable but spot price less than bid price

C Capacity available but spot price higher than bid price

D Capacity unavailable and spot price higher than bid price

💡 Hint

Check columns 'Capacity Available?' and 'Spot Price ($)' vs 'Bid Price ($)' in step 2.

At which step does the Spot Instance get terminated due to price changes?

A Step 3

B Step 4

C Step 5

D Step 6

💡 Hint

Look for 'Instance terminated' in the 'Result' column.

If the bid price was increased to $0.07, how would the termination step change?

A Instance would terminate earlier

B Instance would never terminate

C Instance would terminate later or not at all if price stays below $0.07

D No change in termination

💡 Hint

Compare 'Spot Price ($)' and 'Bid Price ($)' columns in variable_tracker after step 4.

Concept Snapshot

Spot Instances let you use spare AWS capacity at lower cost.
You bid a max price; AWS launches instance if capacity and price allow.
Instance runs until spot price exceeds your bid or capacity is needed.
You save money but risk instance termination.
Use for flexible, interruptible workloads.

Full Transcript

Spot Instances are a way to save money by using spare AWS capacity. You request an instance with a maximum price you are willing to pay. AWS checks if there is capacity and if the current spot price is below your bid. If yes, your instance launches and runs. If the spot price rises above your bid, AWS terminates your instance. This process helps you save costs compared to on-demand instances but comes with the risk of interruption. The execution table shows each step from request to termination and cost savings.

Practice

1. What is the main benefit of using Spot Instances in AWS?

easy

A. They offer unlimited storage space for your data.

B. They guarantee 24/7 uptime without interruptions.

C. They automatically scale your application based on traffic.

D. They provide significant cost savings by using spare capacity.

Solution

1. Step 1: Understand Spot Instances purpose

   Spot Instances use spare AWS capacity and are cheaper but can be interrupted.

2. Step 2: Compare options

   Only They provide significant cost savings by using spare capacity. mentions cost savings from spare capacity, others describe unrelated features.

3. Final Answer:

   They provide significant cost savings by using spare capacity. -> Option D

4. Quick Check:

   Spot Instances = Cost savings [OK]

Hint: Spot Instances save money by using spare capacity [OK]

Common Mistakes:

• Thinking Spot Instances guarantee uptime
• Confusing Spot Instances with auto-scaling
• Assuming Spot Instances provide extra storage

2. Which of the following is the correct way to request a Spot Instance using AWS CLI?

easy

A. aws ec2 request-spot-instances --spot-price 0.05 --instance-count 1 --type t3.micro

B. aws ec2 create-spot-instance --price 0.05 --count 1 --instance-type t3.micro

C. aws ec2 spot-instance-request --max-price 0.05 --count 1 --instance t3.micro

D. aws ec2 launch-spot-instance --price 0.05 --number 1 --type t3.micro

Solution

1. Step 1: Identify correct AWS CLI command

   The correct command is aws ec2 request-spot-instances with parameters like --spot-price, --instance-count, and --type.

2. Step 2: Check options for syntax correctness

   Only aws ec2 request-spot-instances --spot-price 0.05 --instance-count 1 --type t3.micro uses the correct command and parameter names as per AWS CLI documentation.

3. Final Answer:

   aws ec2 request-spot-instances --spot-price 0.05 --instance-count 1 --type t3.micro -> Option A

4. Quick Check:

   Correct CLI syntax = aws ec2 request-spot-instances --spot-price 0.05 --instance-count 1 --type t3.micro [OK]

Hint: Use 'aws ec2 request-spot-instances' with correct flags [OK]

Common Mistakes:

• Using wrong command names like create-spot-instance
• Incorrect parameter names like --price instead of --spot-price
• Mixing instance count and type flags

3. Consider this AWS CLI command output snippet after requesting Spot Instances:

{
  "SpotInstanceRequests": [
    {
      "SpotInstanceRequestId": "sir-12345",
      "State": "active",
      "Status": {"Code": "fulfilled", "Message": "Your Spot request is fulfilled."},
      "InstanceId": "i-67890"
    }
  ]
}

What does this output indicate?

medium

A. The Spot Instance request is active and the instance is running.

B. The Spot Instance request was denied due to price limits.

C. The Spot Instance request is pending and waiting for capacity.

D. The Spot Instance request was cancelled by the user.

Solution

1. Step 1: Analyze the 'State' and 'Status' fields

   The state is "active" and status code is "fulfilled", meaning the request succeeded and instance launched.

2. Step 2: Interpret the meaning of 'InstanceId'

   The presence of an InstanceId means the Spot Instance is running.

3. Final Answer:

   The Spot Instance request is active and the instance is running. -> Option A

4. Quick Check:

   State active + fulfilled = running instance [OK]

Hint: Active state and fulfilled status mean instance is running [OK]

Common Mistakes:

• Confusing 'active' with 'pending'
• Ignoring the 'fulfilled' status message
• Assuming InstanceId is missing means failure

4. You wrote this JSON snippet to request a Spot Instance but it fails:

{
  "InstanceCount": 1,
  "Type": "one-time",
  "LaunchSpecification": {
    "InstanceType": "t3.micro",
    "ImageId": "ami-0abcdef1234567890"
  }
}

What is the likely error causing the failure?

medium

A. Wrong Type value; should be "persistent" only.

B. Missing the SpotPrice field to set max price.

C. Incorrect InstanceCount value; must be zero.

D. Invalid ImageId format; must be numeric only.

Solution

1. Step 1: Check required fields for Spot Instance request

   Spot requests require a SpotPrice to specify max price willing to pay.

2. Step 2: Validate other fields

   InstanceCount of 1 is valid, Type can be "one-time", and ImageId format is correct.

3. Final Answer:

   Missing the SpotPrice field to set max price. -> Option B

4. Quick Check:

   SpotPrice required for request [OK]

Hint: SpotPrice is mandatory in Spot Instance requests [OK]

Common Mistakes:

• Omitting SpotPrice field
• Using invalid Type values
• Misunderstanding ImageId format

5. You want to run a batch job on AWS using Spot Instances to save costs. The job can be interrupted and resumed later. Which strategy best balances cost savings and job completion?

hard

A. Use Reserved Instances for guaranteed availability.

B. Request On-Demand Instances only to avoid interruptions.

C. Request Spot Instances with a low max price and use checkpointing to save progress.

D. Request Spot Instances with the highest max price to avoid interruptions.

Solution

1. Step 1: Understand workload tolerance

   The batch job can handle interruptions and resume, so Spot Instances are suitable.

2. Step 2: Choose cost-effective and reliable approach

   Setting a low max price saves money but risks interruptions; checkpointing allows resuming work safely.

3. Step 3: Evaluate other options

   On-Demand and Reserved Instances cost more and don't leverage Spot savings; highest max price reduces savings.

4. Final Answer:

   Request Spot Instances with a low max price and use checkpointing to save progress. -> Option C

5. Quick Check:

   Interruptible job + low price + checkpointing = best cost savings [OK]

Hint: Use low max price + checkpointing for interruptible jobs [OK]

Common Mistakes:

• Choosing On-Demand or Reserved ignoring cost savings
• Setting max price too high losing savings
• Not implementing checkpointing for interruptions