As the lead cloud architect for a global e-commerce platform, you are tasked with deploying a highly available web application on Azure. The application must not only handle unpredictable traffic spikes during peak shopping seasons but also ensure zero downtime during planned maintenance windows. Additionally, the solution must comply with PCI DSS standards for payment processing and optimize cost without compromising performance. Considering these requirements, which Azure compute service would you recommend for the deployment, and why? (Choose the BEST option.)