Which service should a solutions architect recommend?

Explanations:

Amazon Aurora MySQL requires selecting a specific instance type and is not designed to automatically scale with fluctuating workloads. It may not be the best choice for infrequent access patterns with uncertain future load.

Amazon Aurora Serverless for MySQL allows for automatic scaling based on demand, making it ideal for infrequent access patterns. It minimizes costs during low usage and can handle spikes in traffic seamlessly, ensuring minimal downtime for the sales team.

Amazon Redshift Spectrum is a service for querying data stored in Amazon S3 using SQL but is not suitable for a transactional database workload like the one described. It is primarily used for analytics rather than operational databases.

Amazon RDS for MySQL does require selecting a specific instance type and is more suited for steady workloads rather than infrequent access patterns. It does not provide the automatic scaling feature that would benefit the sales team’s needs for minimal downtime with variable access patterns.