Amazon Kinesis Data Streams in on-demand mode is purpose-built for real-time ingestion of streaming data and scales automatically with traffic, which is ideal for fluctuating workloads like clickstream data.
Combined with AWS Lambda, which scales concurrently based on incoming events, this setup ensures efficient, real-time processing with minimal configuration and cost overhead.
Option B involves Firehose, which is not optimal for low-latency processing. Option C is incorrect as Kinesis Video Streams is designed for video data, not clickstream. Option D introduces Flink, which adds unnecessary complexity when Lambda suffices.

AWS WAF allows web applications to protect themselves from common web exploits and vulnerabilities.
Using AWS managed rule groups ensures protection against known attack patterns, such as SQL injection and cross-site scripting. Associating AWS WAF with the ALB provides application-layer security and real-time threat mitigation.
Reference: AWS Documentation - AWS WAF and Shield Developer Guide

Amazon EFS allows automatic transitions to Infrequent Access (IA) and back to Standard when accessed again using the lifecycle policy.
By specifying the bursting throughput mode, throughput scales automatically with file system size.
"With EFS Lifecycle Management, you can automatically move files to EFS Infrequent Access storage and automatically return them to Standard storage when accessed."
"The Bursting Throughput mode scales with your file system size."
- Amazon EFS Lifecycle Management
This option matches all requirements:
* Auto transition to IA after 30 days.
* Auto transition back to Standard on access.
* Bursting throughput for scaling with file system size.

The most cost-effective and scalable solution for generating thumbnails when photos are uploaded to an S3 bucket is to useS3 event notificationsto trigger anAWS Lambda function. This approach avoids the need for a long-running EC2 instance or EMR cluster, making it highly cost-effective because Lambda only charges for the time it takes to process each event.
S3 Event Notifications: Automatically triggers the Lambda function when a new photo is uploaded to the S3 bucket.
AWS Lambda: A serverless compute service that scales automatically and only charges for execution time, which makes it the most economical choice when dealing with periodic events like photo uploads.
The Lambda function can generate the thumbnail and upload it to a second S3 bucket, fulfilling the requirement efficiently.
Option AandOption B(EMR or EC2 with scheduled scripts)**: These are less cost-effective as they involve continuously running infrastructure, which incurs unnecessary costs.
Option D (S3 Storage Lens): S3 Storage Lens is a tool for storage analytics and is not designed for event- based photo processing.
AWS References:
Amazon S3 Event Notifications
AWS Lambda Pricing

For near-real-time streaming workloads that are highly latency-sensitive, the network layer must provide ultra- low latency and high throughput between compute nodes. Elastic Fabric Adapter (EFA) is specifically designed to meet these requirements. EFA enables EC2 instances to communicate using a high-performance network interface that bypasses traditional TCP/IP networking, providing lower and more consistent latency.
This is especially valuable for tightly coupled workloads that require fast inter-node communication.
Option B is the correct choice because EFA supports custom networking stacks and is optimized for applications such as real-time data processing, distributed computing, and high-performance workloads. EFA integrates directly with supported EC2 instance types and allows applications to take advantage of enhanced networking capabilities without requiring complex multi-VPC architectures.
Option A introduces additional network hops and latency due to VPC peering and is not suitable for ultra-low- latency workloads. Option C (spread placement groups) is designed to increase fault tolerance by placing instances on separate hardware, but it does not optimize for low-latency communication and may actually increase network distance between instances. Option D improves storage performance, not network performance, and does not affect inter-instance latency.
Therefore, B is the best solution because Elastic Fabric Adapter is the AWS-recommended approach for achieving the lowest possible network latency between EC2 instances in performance-critical streaming architectures.