What Is It?
VM Auto Scaling automatically adjusts the number of VM instances based on demand. Define scaling policies based on metrics (CPU utilization, network traffic) to scale out during high traffic and scale in during low usage. The service integrates with the Managed Application Load Balancer (ALB), automatically registering and deregistering scaled instances with ALB target groups to distribute traffic; VM Auto Scaling has no equivalent automatic integration with the Managed Network Load Balancer (NLB).
Quick Facts
| Aspect | Details |
|---|---|
| Type | Automatic VM instance scaling service |
| Scaling Direction | Scale out (increase) and scale in (decrease) |
| Trigger Types | Metric-based (CPU utilization, network traffic) |
| Integration | Managed ALB, Managed NLB |
| Target Resources | Compute Engine VM replicas in Auto Scaling Groups |
| Management | DCD, Cloud API |
What You Can Do
Metric-Based Scaling
Define scaling policies based on CPU utilization or network traffic metrics (incoming/outgoing bytes or packets). Automatically add instances when thresholds are exceeded and remove them when demand decreases.
Policy-Based Scaling Configuration
Configure metric-based scaling policies with customizable evaluation intervals and cooldown periods. Scale out before anticipated traffic spikes and scale in during known quiet periods.
Integration with Load Balancers
Automatically register and deregister new instances with Managed ALB target groups. Traffic distributes to scaled instances without manual configuration; no equivalent automatic registration exists for the Managed Network Load Balancer (NLB).
Capacity Planning
Define minimum and maximum instance counts to ensure baseline capacity while capping costs. Scaling actions always remain within these defined boundaries.
Auto Scaling Groups
Group Compute Engine VM replicas into Auto Scaling Groups with shared configuration. All instances in the group scale together and are managed uniformly according to the defined scaling policies.
Replica Management
Configure minimum and maximum replica counts; the service adds or removes replicas only when a configured scaling policy (metric-based threshold or manual action) is triggered. VM Auto Scaling does not independently detect and replace an individual failed or terminated replica outside of a triggered scaling action.
Best For
| Scenario | Why It Fits |
|---|---|
| Variable traffic applications | Automatically handle traffic spikes and quiet periods |
| Cost optimization | Scale down during low usage to reduce running instance costs |
| High availability | Maintain minimum instance count for redundancy (VM Auto Scaling is currently in Early Access; IONOS recommends limiting production-critical high-availability use until General Availability) |
| Predictable patterns | Pre-scale capacity through policy tuning |
| Event-driven workloads | Scale out for promotions, launches, or seasonal peaks |
| Development/staging environments | Scale to minimum of one instance during off-hours to minimize costs (scale-to-zero is not supported) |
Key Considerations
Billing & Costs
- Main billing: Billed for the running VM replica instances
- Scaling costs: Pay only for instances while they run
- No Auto Scaling service fee: No separate charge for scaling functionality
Limitations
- Scaling is horizontal only: it adds and removes VM replicas and does not vertically resize a running VM. Replica configuration changes apply to new replicas, not to existing ones
- Can optionally integrate with Managed ALB or NLB for traffic distribution (recommended but not required)
- Minimum and maximum instance limits must be defined
- Scaling actions have cooldown periods to prevent rapid oscillation
- Metric-based scaling depends on monitoring data availability
- Scale-to-zero is not supported
Management Options
- Data Center Designer (DCD)
- Cloud API
- Configure Auto Scaling Groups
- Define metric-based scaling policies (one metric policy per group)
- Set minimum and maximum replica counts (the actual count is managed automatically by the service)