---
title: 'Schema deployment and migrations'
description: 'Change a schema deliberately and verify its effect on data.'
---

# Schema deployment and migrations

Schema deployment updates the backend model. Application deployment updates Studio and server tools. Coordinate both when a feature needs new fields and new UI.

Many deployments are the second half of a question you could not answer yet: add the field or relationship, deploy, then backfill. The design loop is in [iterating your schema](/docs/schema/iterating-your-schema).

## Safe change workflow

1. Commit the current configuration and identify the target project.
2. Export and validate the data you need using the [public CLI](/docs/guides/import-export).
3. Develop the change in a disposable project first.
4. Run [CLI deploy](/docs/cli/deploy), inspect validation and completion, and stop if it fails.
5. Refresh Explorer's schema and check representative reads and writes.
6. Publish the matching application configuration.

## Breaking changes

Removing an entity or attribute and changing a data type can cause validation errors or data loss. Follow the specific [schema error](/docs/errors/schema) guide rather than forcing deployment blindly.

For a type migration, prefer adding a new field, transforming and checking data, updating consumers, and only then retiring the old field through the supported removal process. Test relationships and scoped values as well as simple scalar values.

Reverting code does not restore removed data. An export must be validated for its actual contents before you rely on it for recovery. Inspect [deployment](/docs/deployment) for application and tool rollout checks.


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