Which AWS purchasing option should the company choose to meet these requirements?

Explanations:

Dedicated Hosts are physical servers dedicated to your use, providing greater control over your compute resources but are generally more expensive and not designed specifically for optimizing long-term costs compared to other options.

Compute Savings Plans offer significant cost savings on AWS compute usage (including Lambda and EC2) in exchange for a commitment to a consistent amount of usage for a 1- or 3-year term. This option provides flexibility and is suitable for optimizing long-term compute costs.

Reserved Instances provide a discounted hourly rate compared to on-demand pricing in exchange for a commitment to a specific instance type in a specific region. While beneficial for steady-state workloads, they lack the flexibility offered by Compute Savings Plans, particularly for optimizing costs across different services like Lambda.

Spot Instances allow users to bid on unused EC2 capacity at potentially lower prices, but they are not reliable for long-term computing needs as instances can be terminated by AWS when the demand for capacity rises. This option is more suited for non-critical workloads rather than long-term cost optimization.