This solution provides a cost-effective and highly available approach to meet the application's needs:
Reserved instances are a good fit for the ten midsize instances that run most of the day, as they are typically offered at a discounted rate and are guaranteed.
During peak hours, pay-as-you-go instances can be added to handle the additional six instances required. This ensures scalability without committing to additional reserved capacity for off-peak times, which helps in reducing costs.