How Do You Change an EC2 Instance Type from t3.large to Compute Optimized?
A company has an Amazon EC2 instance that has high CPU utilization. The EC2 instance is a t3.large instance and is running a test web application. The company discovers that the web application would operate better on a compute optimized large instance. What should a CloudOps engineer do to make this change?
Community Insight
The test is whether you know the instance-type change lifecycle for EBS-backed instances; the trap is assuming you can resize a running instance or that hibernation plays a role in the resize.
Changing an EC2 instance's type — such as moving a t3.large test web server to a compute optimized instance — requires stopping the instance, applying the new instance type, and starting it again. This page confirms why the stop-change-start sequence (C) is the only supported path and why VM Import/Export, hibernation and live resizing are not.
Many candidates pick option D, assuming a running EC2 instance can be resized in place like a container or Lambda memory setting; EC2 instance types are tied to the underlying host hardware and the instance must be stopped first.
Community Discussion (1 comments)
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Expert Analysis
Why the Answer Is Correct
EC2 instance types map to specific CPU, memory and network hardware, so the type can only be reassigned while the instance is not running on a host. For an EBS-backed instance, the supported workflow is exactly what option C describes: stop the instance, change the instance type (console, CLImodify-instance-attribute --instance-type, or API), then start it on new hardware. Because the root volume is EBS-backed, the data persists across the stop/start, and the elastic IP or public IP behavior is predictable (public IPv4 may change unless an Elastic IP is attached). Moving from t3.large to a compute optimized family such as c7i.large directly addresses the high CPU utilization the test web application is exhibiting. The learner comment from Bad_Mat reaches the same conclusion, stating "Stop the EC2 instance. Change the instance type to a compute optimized instance."Why the Other Options Are Wrong
Option A is a category error: AWS VM Import/Export migrates VM images from on-premises hypervisors into EC2 as AMIs; it is not a mechanism for resizing an instance that already lives in AWS. Option B adds hibernation, which preserves RAM contents to EBS on stop and restores it on start — it does not remove the stop/start requirement, and hibernation has its own prerequisites (encrypted root volume, supported instance families, size limits). Option D is the classic trap: an instance type cannot be changed while the instance is in the running state; the console and API both reject the request until the instance is stopped. None of A, B or D can produce a compute optimized instance for a running t3.large.Community Comment Notes
Bad_Mat's comment is short but aligns with the documented procedure, explicitly selecting the stop-change-start answer. The comment reinforces that the community treats the resize as a stop/start operation rather than an in-place or import operation. There is no dissent in the thread, so the consensus here matches both the wording of the question and AWS's documented behavior for EBS-backed instances.Official Reference
Exam Strategy
When a stem mentions changing an instance's size, family or type, immediately look for the stop-change-start option and eliminate anything claiming a live resize. Remember that hibernation and VM Import/Export are different features, not shortcuts around the stop/start requirement.
Frequently Asked Questions
Can an EC2 instance type be changed while the instance is running?
No. The instance must be stopped (not terminated) before the type can be modified; the new type takes effect when you start it again.
Why doesn't enabling hibernation help change the instance type?
Hibernation only preserves RAM contents to the EBS root volume across a stop/start; the instance still must be stopped to change its type, so hibernation adds no benefit here.
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