An e-commerce company is utilizing AWS Elastic Beanstalk to host its application, with an Auto Scaling group maintaining three Amazon EC2 instances. The application's performance is greatly affected if the instance count drops below two. Currently, the company uses the default all-at-once deployment policy. Considering these factors, the company seeks a more cost-effective deployment strategy for future updates.

Which of the following represents the most cost-effective deployment strategy for the company?