For an always-on, appropriately sized database server needed for one year, which Amazon EC2 pricing option delivers the greatest cost savings?

Standard Reserved Instances (RIs) offer the greatest cost savings for a continuously running, appropriately sized database server over a one-year term. RIs provide a significant discount (up to 75%) compared to On-Demand pricing in exchange for committing to a specific instance type and region for a 1-year or 3-year term. On-Demand Instances are more expensive as they offer no commitment or discount, making them unsuitable for a steady-state workload. Convertible Reserved Instances offer flexibility to change instance families, operating systems, or tenancy, but typically provide slightly less discount than Standard RIs, making them not the greatest savings for a fixed requirement. Spot Instances are the cheapest but are not suitable for an "always-on" database server because they can be interrupted with two minutes' notice when EC2 needs the capacity back.