What is Azure Virtual Machine Scale Sets (VMSS) and why are they used?

Azure Virtual Machine Scale Sets (VMSS) allow organizations to deploy and manage a group of virtual machines as a scalable unit. Instead of manually creating and managing individual VMs, administrators can define a VM-based workload and allow Azure to manage multiple instances. VM Scale Sets are useful for applications that need: Horizontal scaling High availability Multiple VM instances Automatic scaling based on demand Consistent VM configurations Load distribution For example, if a web application normally requires four VM instances but traffic increases significantly, a scale set can increase the number of instances based on defined scaling rules. When demand decreases, instances can be reduced to control costs. VMSS can be combined with load-balancing technologies so incoming traffic is distributed across available instances. A typical architecture could be: Users → Load Balancer → VM Scale Set → Application Instances Administrators should consider scaling rules, VM image management, networking, health monitoring, availability, security, patching, and cost optimization when designing a VMSS architecture. VMSS is particularly valuable when an application needs multiple VM instances that can scale horizontally while maintaining a consistent infrastructure configuration.