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The schema registry, a feature of Azure Device Registry, is a synchronized repository that's accessible both in the cloud and at the edge. It stores definitions of messages coming from edge assets and exposes an API to access those schemas from either location.
This article helps you decide:
- When to create a new schema registry or reuse an existing one.
- Best practices for schema registry sharing.
Service applicability
Schema registries are currently used only in Azure IoT Operations scenarios, where data flows use schemas to describe, transform, and serialize messages. The schema registry is accessible both at the edge and in the cloud, enabling consistent schema management across your solution.
| Feature | Azure IoT Operations | Azure IoT Hub |
|---|---|---|
| Schema registries | GA | Not applicable |
For more information about schema registries, see Understand message schemas.
Cardinality rules
- Each Azure IoT Operations instance maps to exactly one schema registry.
- Multiple Azure IoT Operations instances can share the same schema registry.
- A schema registry is scoped to an Azure resource group and backed by an Azure Storage account.
Sharing a schema registry within organizational or site boundaries is the recommended default. Create a separate registry only when schemas are genuinely independent or when different storage accounts are required.
When to create a new schema registry
Create a new schema registry only when the schemas are genuinely independent, for example:
- Completely separate sites with no shared asset types or message formats.
- Different storage accounts are required for schema storage at different sites.
When to reuse an existing schema registry
In most cases, reuse an existing schema registry:
- Multiple Azure IoT Operations instances at the same site should share one schema registry. Message schemas logically originate from the assets and devices at a site, so there's no meaningful benefit to creating a separate registry for each instance.
- Sites with overlapping asset types benefit from sharing schemas rather than duplicating them across registries.
Best practices for schema registry sharing
| Best practice | Why | How |
|---|---|---|
| Share a common schema registry within organizational or site boundaries | Avoids unnecessary duplication and reduces management overhead. Schemas logically belong to the assets and devices at a site, not to individual instances. | When you deploy multiple Azure IoT Operations instances at the same site, point them all to the same schema registry. |
| Review deployment defaults before accepting them | Azure IoT Operations deployment scripts prompt you to create a new schema registry, which can lead to unintended proliferation. | During deployment, specify an existing schema registry if one already exists for your site or organizational boundary. |
Planning constraints and limits
The following limit affects schema registry design. For the full list, see Azure Device Registry limits.
| Resource | Limit |
|---|---|
| Schema registries per subscription | 100 |