The best combination of solutions is: Use Amazon CloudFront to cache and deliver the video content globally, reducing latency and improving streaming performance and Use Amazon Elastic Transcoder to reformat the raw video clips into mobile-friendly, compressed formats optimized for streaming.

Amazon CloudFront is a global content delivery network (CDN) that caches content at edge locations near users. By placing CloudFront in front of the S3 bucket, video files can be delivered faster, with reduced latency and buffering. This is essential for media-rich applications, especially for mobile users.

Amazon Elastic Transcoder is a managed service that automatically converts media files into formats that are suitable for various devices and resolutions. Raw video files are typically large and inefficient for mobile streaming. Transcoding them into optimized formats (e.g., H.264 in MP4 containers) helps reduce load times, improves playback experience, and conserves bandwidth.

The option Implement AWS DataSync to copy the video content to S3 buckets in different AWS Regions for improved global access does not address the real issuefile size and delivery latency. While replicating data might reduce cross-region transfer times, it wont solve performance problems caused by large raw files or help with mobile optimization.

The option Set up an Auto Scaling group of EC2 instances in AWS Local Zones to serve as edge servers and cache video files for faster delivery introduces unnecessary complexity and operational overhead. CloudFront already provides caching and edge delivery in a fully managed, cost-effective way. Managing EC2 instances at edge locations would increase costs and administrative burden without delivering superior benefits.

The option Launch an Auto Scaling group of EC2 instances to run custom transcoding software for converting the video files is viable but not ideal. Using EC2 requires managing the software, infrastructure, and scaling. Elastic Transcoder or even AWS Elemental MediaConvert (in advanced scenarios) are managed services that remove operational complexity and scale automatically.

This question is valuable because it evaluates your ability to design scalable, low-latency, media-centric applications in AWS using managed services. A common exam trick is to include multiple viable-sounding compute-heavy options that actually increase complexity. Look for answers that use fully managed services like CloudFront and Elastic Transcoder to offload infrastructure tasks while solving the core problem: performance and mobile optimization.

The challenge here is identifying both the need to reduce file sizes (via transcoding) and deliver them faster (via a CDN). Many candidates focus only on one of these layers. Thinking holistically about performance, bandwidth, and end-user experience is key to choosing the right combination.

Full AWS Practitioner Certification Question