What feature in Azure allows for automatic scaling of database resources based on demand?

The feature that allows for automatic scaling of database resources based on demand in Azure is Elastic Pools. Elastic Pools are designed to manage multiple databases that have varying and unpredictable usage patterns. They enable multiple databases to share resources like CPU and memory, which makes it more efficient and cost-effective.

When demand increases for a specific database, Azure can automatically allocate additional resources from the pool to accommodate the workload without requiring manual intervention. This ensures that performance remains consistent during peak times while also optimizing resource utilization during lower usage periods. Consequently, organizations benefit from a scalable solution that adjusts to current needs without incurring unnecessary costs.

In contrast, sharding involves distributing data across multiple databases or servers to improve performance and scalability, but it does not automatically adjust resources based on demand. Database replicas are used primarily for redundancy, high availability, and load balancing, whereas a Backup Vault provides a centralized location for managing backup resources but lacks the capability for dynamic resource allocation.