Q2: What is the difference between stopping and terminating an EC2 instance?

This is a very common real-time production interview question, especially for DevOps and Cloud Engineer roles.

Detailed Explanation

1. Stopping an EC2 Instance

When you stop an EC2 instance:

• The instance shuts down gracefully (like normal OS shutdown).

• The EBS root volume remains attached.

• You can start the instance again later.

• The instance ID remains the same.

• The private IP remains the same.

• The public IP changes (unless Elastic IP is attached).

• You are charged only for:

  • EBS storage

  • Elastic IP (if attached and not used properly)

• You are not charged for compute hours while stopped.

What happens technically?

AWS releases the underlying host machine, but keeps your EBS volume data intact.

2. Terminating an EC2 Instance

When you terminate an EC2 instance:

• The instance is permanently deleted.

• The instance ID is gone forever.

• The root EBS volume is deleted by default (unless “Delete on Termination” is unchecked).

• You cannot restart or recover the instance.

• All attached instance store data is lost permanently.

• Billing for compute and storage stops (except retained volumes/snapshots).

Comparison Table

Production Scenarios

Scenario 1: Cost Optimization

In many companies:

• Dev/Test servers are stopped at 8 PM daily using Lambda automation.

• They are restarted next morning.

• This reduces EC2 compute cost by 40–50%.

Stopping is ideal here.

Scenario 2: Application Upgrade Testing

Before upgrading an application:

• Engineers stop the instance.

• Take a snapshot.

• Restart for testing.

If something breaks, they can recover easily.

Scenario 3: Decommissioning Server

When a project ends:

• Instance is terminated.

• Manual snapshot taken before termination.

• Instance removed permanently to avoid cost leak.

Terminate is ideal here.

Important Interview Edge Points

If the root volume has DeleteOnTermination = false, EBS volume will survive even after termination.

Instance Store data is always lost on stop or terminate.

If you want static public IP after restart → use Elastic IP.

Stopped instances still consume:

• EBS cost

• Snapshot cost

• Elastic IP cost (if not attached properly)

Interview One-Line Answer

“Stopping an EC2 instance preserves the EBS volume and allows restart later, while terminating permanently deletes the instance and its associated root volume.”