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Applies to: 
Azure SQL Database
Serverless is a compute tier for single databases in Azure SQL Database that automatically scales compute based on workload demand and bills for the amount of compute used per second. The serverless compute tier also automatically pauses databases during inactive periods when only storage is billed and automatically resumes databases when activity returns. The serverless compute tier is available in the General Purpose service tier and the Hyperscale service tier.
Currently, auto-pause and auto-resume are only supported in the General Purpose service tier.
Overview
A compute autoscaling range and an auto-pause delay are important parameters for the serverless compute tier. The configuration of these parameters shapes the database performance experience and compute cost.
Performance configuration
- The minimum vCores and maximum vCores are configurable parameters that define the range of compute capacity available for the database. Memory and IO limits are proportional to the vCore range specified.
- The auto-pause delay is a configurable parameter that defines the period of time the database must be inactive before it's automatically paused. The database is automatically resumed when the next login or other activity occurs. Alternatively, you can disable automatic pausing. For more information, see Auto-pause and auto-resume in the serverless compute tier for Azure SQL Database.
Default settings
The following table shows the available values for these parameters.
| Parameter | Value choices | Default value |
|---|---|---|
| Minimum vCores | Depends on maximum vCores configured - see resource limits. | 0.5 vCores |
| Auto-pause delay | Minimum: 15 minutes Maximum: 10,080 minutes (seven days) Increments: 1 minute Disable auto-pause: -1 |
60 minutes |
Cost
The cost for a serverless database is the sum of the compute cost and storage cost. The storage cost is determined in the same way as in the provisioned compute tier.
- When compute usage is between the minimum and maximum limits you configure, the compute cost is based on vCore and memory used.
- When compute usage is below the minimum limits you configure, the compute cost is based on the minimum vCores and minimum memory configured.
- When the database is paused, the compute cost is zero and only storage costs are incurred.
For more cost details, see Serverless compute tier billing and cost scenarios.
Scenarios
Serverless is price-performance optimized for single databases with intermittent, unpredictable usage patterns that can afford some delay in compute warm-up after idle usage periods. In contrast, the provisioned compute tier is price-performance optimized for single databases or multiple databases in elastic pools with higher average usage that can't afford any delay in compute warm-up.
Scenarios well suited for serverless compute
- Single databases with intermittent, unpredictable usage patterns interspersed with periods of inactivity, and lower average compute utilization over time.
- Single databases in the provisioned compute tier that are frequently rescaled and customers who prefer to delegate compute rescaling to the service.
- New single databases without usage history where compute sizing is difficult or not possible to estimate before deployment in an Azure SQL Database.
Scenarios well suited for provisioned compute
- Single databases with more regular, predictable usage patterns and higher average compute utilization over time.
- Databases that can't tolerate performance trade-offs resulting from more frequent memory trimming or delays in resuming from a paused state.
- Multiple databases with intermittent, unpredictable usage patterns that can be consolidated into elastic pools for better price-performance optimization.
Compare compute tiers
The following table summarizes distinctions between the serverless compute tier and the provisioned compute tier:
| Serverless compute | Provisioned compute | |
|---|---|---|
| Database usage pattern | Intermittent, unpredictable usage with lower average compute utilization over time. | More regular usage patterns with higher average compute utilization over time, or multiple databases using elastic pools. |
| Performance management effort | Lower | Higher |
| Compute scaling | Automatic | Manual |
| Compute responsiveness | Lower after inactive periods | Immediate |
| Billing granularity | Per second | Per hour |
Purchasing model and service tier
The following table describes serverless support based on purchasing model, service tiers, and hardware:
| Category | Supported | Not supported |
|---|---|---|
| Purchasing model | vCore | DTU |
| Service tier | General Purpose Hyperscale |
Business Critical |
| Hardware | Standard-series (Gen5) | All other hardware |
Auto-scale serverless databases
For more information about auto-scaling and the responsiveness of the serverless compute tier, see Serverless compute tier auto-scaling for Azure SQL Database.
Auto-pause and auto-resume
For detailed information about auto-pause and auto-resume behavior, triggers, troubleshooting, and connectivity, see Auto-pause and auto-resume in the serverless compute tier.
Create a new serverless database
For step-by-step instructions on creating, moving, and configuring serverless databases using the Azure portal, PowerShell, Azure CLI, and T-SQL, see Create and configure a serverless database.
Serverless compute tier best practices
Consider the following best practices when using serverless databases.
Implement application retry logic
All cloud-connected applications should use connection retry logic recommendations. Transient connectivity errors must be handled with retry logic in all cloud applications. Retry logic for serverless databases is especially important because temporary connectivity errors due to auto-resume are predictable.
For more information, see Troubleshooting auto-resume connectivity.
Review interoperability that prevents auto-pause
Some features and settings can prevent a serverless database from auto-pausing. You can disable auto-pause on the database if these features are in use.
For more information, see Troubleshooting auto-pause.
Monitor
For more information on monitoring pause and resume events of your serverless database, see Monitor the serverless compute tier for Azure SQL Database.
Resource limits
For resource limits, see serverless compute tier.
Billing
For detailed billing information, including compute cost calculations, minimum compute bill, and scenario examples for both General Purpose and Hyperscale tiers, see Serverless compute tier billing.
Available regions
For regional availability, see Serverless availability by region for Azure SQL Database.