Correct answer: Integrate Amazon ElastiCache to persist session data in memory.

Amazon ElastiCache (using Redis or Memcached) is a fully managed, low-latency, in-memory data store ideal for storing transient session data. It allows any EC2 instance to access a common session state, which is critical in a dynamic auto scaling environment with distributed workloads. This architecture supports high availability and resilience across Availability Zones.

Why the other options are incorrect:

Enable sticky sessions on the ALB to maintain session affinity: Sticky sessions tie a user to a specific instance, which undermines fault tolerance and breaks when instances are terminated or replaced during scaling events.
Use AWS Systems Manager Session Manager to track user sessions: This tool is meant for secure administrative shell access to EC2, not for handling web application session data.
Generate temporary credentials with AWS STS for each user session: AWS STS issues temporary credentials for authentication, not for managing application session data.

Bottom line: Amazon ElastiCache enables scalable and centralized session storage that aligns well with dynamic EC2-based architectures.

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