Which architecture should a solutions architect recommend for this situation?

Explanations:

AWS Lambda functions are not suitable for applications that require low-latency file access for large sets of files. Additionally, using an instance store volume would not provide the necessary durability and accessibility across multiple instances.

While AWS Lambda can handle parallel processing, it is not ideal for applications requiring low-latency access to a shared file system. An Amazon EBS volume attached to a single EC2 instance cannot be simultaneously accessed by multiple instances, which limits concurrent processing.

Running both applications on a single memory-optimized EC2 instance may lead to resource contention. Although an EBS volume with Provisioned IOPS offers improved performance, it still cannot support concurrent access by multiple applications in the low-latency manner required here.

Configuring two EC2 instances allows both applications to run simultaneously, and using Amazon EFS enables shared access to files with low latency. The General Purpose performance mode and Bursting Throughput mode of EFS are suitable for workloads with variable performance needs, providing the necessary concurrent access and scalability.