Which service is best for improving global load balancing in applications?

Choosing Azure Front Door is the best solution for improving global load balancing in applications because it is specifically designed to optimize web traffic and ensure high availability and performance for applications deployed across multiple geographic locations. Azure Front Door leverages Microsoft's global network to route users to the nearest available instance of an application, effectively distributing traffic based on geographic proximity, response times, and application health.

This service also provides features such as SSL termination, application acceleration, and integrated security measures, enhancing both user experience and application security. The built-in rules engine allows for custom routing and redirection scenarios, which further enhances the capability of managing and fine-tuning the traffic flow.

In contrast, Azure Functions is primarily a serverless compute service focused on executing code in response to events, while Azure DevOps is a set of development tools for software development and project management. Azure Virtual Network provides networking capabilities but does not provide load balancing as its core functionality. Thus, these services do not align with the primary goal of enhancing global load balancing for applications.