A company runs EC2 instances with a stable, continuous load and Lambda functions with variable, unpredictable load. The application uses an Amazon MemoryDB for Redis cluster as a cache. To minimize monthly cost overall, which purchasing strategy should the company adopt?

The correct option minimizes cost by applying the most appropriate purchasing strategy for each service. EC2 Instance Savings Plans offer the deepest discounts for stable, continuous EC2 usage. Compute Savings Plans are flexible and cover Lambda, making them suitable for variable serverless workloads, especially for predictable baseline consumption. MemoryDB for Redis offers reserved nodes, which provide significant cost savings for predictable cache capacity. Incorrect options: Buying a Compute Savings Plan for EC2 instances is less cost-effective than an EC2 Instance Savings Plan for stable workloads. Reserving Lambda concurrency is a scaling control, not a cost-saving purchasing option. A single Compute Savings Plan cannot cover MemoryDB cache nodes, as MemoryDB has its own reserved node purchasing option. Compute Savings Plans do not cover MemoryDB cache nodes. Again, reserving Lambda concurrency is not a cost-saving purchasing option.