Which performance feature of an Amazon EC2 instance is configured to add additional resources based on set trigger points?

Burstable performance instances, such as those in the Amazon EC2 T instance family, are designed to provide a baseline level of CPU performance with the ability to burst to a higher level when required. This feature is managed by a CPU credit system. When the instance's workload is below the baseline threshold, it earns credits. When the workload increases (a trigger point), it spends these credits to temporarily run at a higher performance level. This model is cost-effective for applications with variable or "bursty" workloads that don't consistently need full CPU power, allowing them to add resources dynamically based on demand.

B. Optimized: This refers to instance families built for sustained high performance in a specific area (e.g., CPU-Optimized, Memory-Optimized), not for dynamic bursting based on triggers.
C. Managed: This describes a service model where AWS handles underlying infrastructure or scaling policies, not a specific performance feature of an individual EC2 instance itself.
D. Accelerated: This refers to instances equipped with specialized hardware like GPUs or FPGAs for specific computational tasks, rather than a general-purpose bursting capability.

1. Amazon Web Services (AWS) Documentation. Amazon EC2 User Guide for Linux Instances, "Burstable performance instances." This official documentation states, "Burstable performance instances provide a baseline level of CPU performance with the ability to burst to a higher level when required by your workload... When the instance needs to run at a higher CPU level, it spends the credits that it has accrued."

2. Amazon Web Services (AWS) Documentation. AWS Whitepaper, "An Overview of the AWS Cloud Adoption Framework," Feb 2021. Page 33 discusses rightsizing and mentions burstable instances (T-family) as a cost-optimization strategy for workloads that have "infrequent CPU spikes."

3. Armbrust, M., et al. (2010). "A view of cloud computing." Communications of the ACM, 53(4), 50-58. While a foundational paper, it discusses the principle of elasticity (Section 3.1), where resources are acquired on-demand. Burstable instances are a specific implementation of this principle at the instance level, allowing for fine-grained, automatic resource scaling based on workload triggers. DOI: https://doi.org/10.1145/1721654.1721672

4. Cornell University, CS 5412: Cloud Computing. Lecture 10: Cloud Storage and Compute. Slide 23, "EC2 Instance Types," explicitly categorizes T2/T3 instances as "Burstable, low cost, for bursty workloads," distinguishing them from other types like Compute Optimized (C4) and Memory Optimized (R4).