For predictable baseline usage, Reserved Instances provide a significant discount compared to On-Demand pricing in exchange for a commitment to a consistent amount of compute capacity. To handle the variable peak loads during weekends, On-Demand Instances or Spot Instances can be used. Given the need for availability during peak times, relying solely on Spot Instances which can be interrupted is risky; therefore, a mix of Reserved Instances for the baseline and On-Demand Instances to handle peaks can be the most cost-effective and reliable approach as it provides cost savings for the predictable demand and flexibility to scale with reliable instances during spikes.