Online CLF-C02 Questions Video

Scaling horizontally across multiple Availability Zones is a way to adopt a highly available architecture, as it increases the fault tolerance and resilience of the application. Scaling vertically to a larger EC2 instance size is a way to improve the performance of the application, but it does not improve the availability. Purchasing an EC2 Dedicated Instance is a way to isolate the instance from other AWS customers, but it does not improve the availability. Changing the EC2 instance family to a compute optimized instance is a way to optimize the instance type for the workload, but it does not improve the availability. These concepts are explained in the AWS Well-Architected Framework2.

 Spot Instances are instances that use spare EC2 capacity that is available for up to 90% off the On-Demand price. Because Spot Instances can be interrupted by EC2 with two minutes of notification when EC2 needs the capacity back, you can use them for applications that have flexible start and end times, or that can withstand interruptions5. This option is most cost-effective for the use case described in the question. Reserved Instances are instances that you purchase for a one-year or three-year term, and pay a lower hourly rate compared to On-Demand Instances. This option is suitable for applications that have steady state or predictable usage. Dedicated Instances are instances that run on hardware that’s dedicated to a single customer within an Amazon VPC. This option is suitable for applications that have stringent regulatory or compliance requirements. On-Demand Instances are instances that you pay for by the second, with no long-term commitments or upfront payments. This option is suitable for applications that have unpredictable or intermittent workloads.

 Create annotated documentation is the design principle that is included in the operational excellence pillar of the AWS Well-Architected Framework. According to the AWS Well-Architected Framework whitepaper, creating annotated documentation means "documenting your workload so that the team understands the architecture, how to operate the workload, and how the workload delivers value to customers."3 Anticipate failure, ensure performance efficiency, and optimize costs are design principles that belong to other pillars of the AWS Well-Architected Framework, such as reliability, performance efficiency, and cost optimization.

A is correct because Amazon Lex is the AWS service that helps users build conversational interfaces into applications using voice and text. B is incorrect because Amazon Transcribe is the AWS service that helps users convert speech to text. C is incorrect because Amazon Comprehend is the AWS service that helps users analyze text using natural language processing. D is incorrect because Amazon Timestream is the AWS service that helps users collect, store, and process time series data.