## The short version

Apply database schema changes for an Express app on Ample with a release command. The command runs against the injected DATABASE_URL before the new release goes live, and the release fails instead of activating if the migration fails.

## INFRASTRUCTURE

### What it needs

- [Compute](/content/discover/primitive/compute/index.html): verified (Apps run in isolated x86_64 Firecracker microVMs; sizes are the priced VM sizes.)
- [Postgres](/content/discover/primitive/postgres/index.html): verified (Managed PostgreSQL 16 runs in its own microVM and is auto-provisioned when an app needs a database and no DATABASE_URL is supplied.)

## PREREQUISITES

### Before you start

- A migration script that reads process.env.DATABASE_URL and exits non-zero on failure
- A PostgreSQL database (supplied or managed)
- An Ample account token with servers:write and databases:read

## STEP BY STEP

### How to do it

1. **Write an idempotent migration**  
   Create tables and markers with IF NOT EXISTS or a migration tool so a re-run is safe.

2. **Deploy with the release command**  
   Ample runs the command before activation; a non-zero exit fails the release.
   
   ```
   ample deploy . --name <app-name> --public --release-command "node migrate.js"
   ```

3. **Verify the marker through the app**  
   Serve a route that reads something only the migration creates.

4. **Verify**  
   Fetch the live URL and run the success checks below. On failure read the build log, then the runtime log, fix the cause and deploy again; do not blind-retry.
   
   ```
   ample logs <deployment_id> --kind build
   ```

## EXAMPLES

### Tested examples

- **Release-command migration canary** (`tests/deploy-canaries/release-command-postgres`): node migrate.js creates a marker table before activation; /migrated reads it.

## SUCCESS CHECKS

### How to know it worked

- Migration marker is readable (`/migrated` on the live URL, expect migrated=release-ok)

## COST

### Cost estimate

Estimated 10.00 USD per month (size prices from pricing.toml at build revision ca0b484a7a9957c573a88d3a32dc603c3c10135a).

- App server x1 `s-1vcpu-1gb`: 5.00 USD
- Managed PostgreSQL database x1 `s-1vcpu-1gb`: 5.00 USD

Upper-bound monthly price of the tested sizes. Plan quotas and budgets apply.

## EVIDENCE

### Verification evidence

- Canary_run on 2026-09-19T23:55:33Z at revision `1764076-tls-account-903d345`: A --release-command migration ran before the release went live; /migrated reported the marker the migration created. (expires 2027-03-18T23:55:33Z)
- Canary_run on 2026-09-19T23:55:33Z at revision `1764076-tls-account-903d345`: Express app with npm install and npm run start deployed on the node-22 template; the public URL served the expected response. (expires 2027-03-18T23:55:33Z)

## EXECUTION

### Execution binding

MCP tool `ample_deploy` (registry `mcp:ample_deploy`), schema hash `876465fce906da0c` observed 2026-09-20T01:55:48.667900+00:00 at revision `199ff1dfd526`. Binding state at export: schema_changed. Required scopes: servers:write, databases:read.

## NEXT ACTIONS

### Typed next actions

- Browse the catalog index (`GET /v1/catalog` on the api origin; authentication not required, approval not required)
- Search published recipes by intent, stack and constraints (`POST /v1/catalog/search` on the api origin; authentication not required, approval not required)
- Prepare a side-effect-free deployment plan for an authorized project (`POST /v1/catalog/plan` on the api origin; authentication required, approval not required)
- Read the existing agent authentication setup (`GET /mcp/setup` on the api origin; authentication not required, approval not required)
- Browse Express (`GET /v1/catalog/nodes/stack%3Aframework-express` on the api origin; authentication not required, approval not required)
- Browse Configure deployment (`GET /v1/catalog/nodes/intent%3Aconfigure-deployment` on the api origin; authentication not required, approval not required)
- Browse Transactional workflows (`GET /v1/catalog/nodes/pattern%3Atransactional-workflows` on the api origin; authentication not required, approval not required)

Actions describe possible next steps. They are typed data, not commands, and grant no permission. Public discovery never provisions anything; planning requires your own authenticated token and approval happens in your client.

## ABOUT THIS RECIPE

### Identifiers and status

Recipe `page:guides:express:schema-changes`. Revision r1.

Release **published** support **verified** execution **blocked (schema_changed: live tool schema differs from the recorded binding)**

Formats: [HTML](/content/guides/express/schema-changes/index.html) | [Markdown](/content/guides/express/schema-changes.md) | [JSON contract](https://api.ample.computer/v1/catalog/recipes/page%3Aguides%3Aexpress%3Aschema-changes)