A company has a high-performance application which runs on a custom developed operating system. The system requires additional resources based on an unexpected increase in workload. They have decided to replatform the application and to provide additional capacity before their customers are impacted. Which IBM Cloud solution should they use?

The core requirements are to replatform an application from a custom OS and rapidly add capacity to handle an unexpected workload increase, thereby preventing customer impact. IBM Cloud Virtual Server Instances (VSIs) are the ideal solution because they can be provisioned in minutes, offering the speed and agility needed to respond to such urgent demands. The act of "replatforming" implies moving the application to a new, standard platform (like a VSI with a common Linux or Windows OS), which allows the company to leverage cloud-native features like rapid, flexible scaling. While Bare Metal offers high performance, its provisioning time (hours) is too slow for this urgent scenario.

A. Bare Metal Server: Provisioning takes hours, which is too slow to meet the immediate need to add capacity "before their customers are impacted."
B. LinuxONE Server: This is a specific, high-end hardware platform (IBM Z). The question does not provide any details that would justify choosing this specialized architecture.
D. Hyper Protect Virtual Server: This is a specialized service focused on confidential computing and high security, which are not the primary requirements stated in the scenario.

1. IBM Cloud Documentation - Virtual Servers for VPC Overview: "With IBM Cloud Virtual Servers for VPC, you can create and manage virtual server instances in the IBM Cloud VPC environment with speed, simplicity, security, and agility." It highlights "Fast provisioning" as a key feature, stating instances are provisioned in minutes. This supports the choice of VSI for rapid capacity addition.

Source: IBM Cloud Docs, "IBM Cloud Virtual Servers for VPC overview".

2. IBM Cloud Documentation - Bare Metal Servers for VPC: "Provisioning a bare metal server takes longer than provisioning a virtual server." This statement directly contrasts the provisioning speed with VSIs, confirming that Bare Metal is not suitable for the urgent requirement in the question.

Source: IBM Cloud Docs, "About Bare Metal Servers for VPC".

3. IBM Cloud Documentation - Application Modernization: The concept of "replatforming" (or "rehost with platform services") involves moving an application to a cloud platform to take advantage of cloud capabilities like auto-scaling and managed services, often involving a change in the underlying OS. This supports the interpretation that the custom OS is being replaced, making a standard VSI a suitable target.

Source: IBM Cloud Docs, "Strategies for modernizing applications".