🃏 EC2 Flashcards

Q: What are the four EC2 pricing models?

A: On-Demand, Reserved Instances, Savings Plans, and Spot Instances.

Q: What is an EC2 placement group of type "Cluster"?

A: Instances placed in a single AZ for low-latency, high-throughput networking. Ideal for HPC workloads.

Q: What is the difference between instance store and EBS?

A: Instance store is ephemeral (lost on stop/terminate) with high IOPS. EBS is persistent block storage that survives instance stop.

Q: What is EC2 Hibernation?

A: Saves the in-memory (RAM) state to the EBS root volume. On restart, the instance resumes from where it left off. Root volume must be encrypted.

Q: What is the maximum number of instances in a Spread placement group per AZ?

A: 7 instances per AZ.

Q: What is User Data in EC2?

A: A script that runs once at instance launch (as root) to automate configuration tasks like installing software.

Q: How do you access EC2 instance metadata?

A: HTTP GET to http://169.254.169.254/latest/meta-data/

Q: What is the difference between Dedicated Hosts and Dedicated Instances?

A: Dedicated Hosts give you a physical server with visibility into sockets/cores (needed for BYOL). Dedicated Instances run on hardware dedicated to your account but without socket/core visibility.

Q: What is ENI vs ENA vs EFA?

A: ENI: basic networking. ENA: Enhanced Networking up to 100 Gbps. EFA: Elastic Fabric Adapter for HPC and MPI workloads.

Q: When should you use Spot Instances?

A: For fault-tolerant, flexible workloads like batch processing, data analysis, CI/CD, and stateless web servers. Not for critical or persistent workloads.