## The short version

Schema changes for a Starlette app on Ample.

WHAT WAS VERIFIED

Verified on Starlette: a --release-command migration ran before activation and its marker was readable by the live app (migrated=release-ok). Build and start: pip install into .ample/python from requirements.txt, then uvicorn from run.py reading PORT on the python-3.12 template.

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 Starlette project (pip install into .ample/python from requirements.txt, then uvicorn from run.py reading PORT on the python-3.12 template)
- A PostgreSQL driver reading DATABASE_URL at runtime
- An Ample account token with servers:write, databases:read

STEP BY STEP

## How to do it

1. 1

### Build and start

pip install into .ample/python from requirements.txt, then uvicorn from run.py reading PORT on the python-3.12 template; the server must bind 0.0.0.0 on PORT.

2. 2

### Run migrations as the release command

Ample runs the command before activation and fails the release if it exits non-zero; keep migrations idempotent.

```
ample deploy . --name <app-name> --public --start "python3 run.py" --release-command "python3 migrate.py"
```

3. 3

### Verify

Fetch the live URL and /p/migrated on the example; on failure read the build and runtime logs.

```
ample logs <deployment_id> --kind build
```

EXAMPLES

## Tested examples

- **Starlette pattern fixture** (`tests/deploy-canaries/starlette-patterns`): Verified schema changes on Starlette.

SUCCESS CHECKS

## How to know it worked

- app responds on its public URL (`/` on the live URL, expect ample canary starlette patterns)
- migrated check from the example (`/p/migrated` on the live URL, expect see the pattern fixture checks)

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. Buckets are allocation-priced per quota and not included.

EVIDENCE

## Verification evidence

- canary_run on 2026-09-21T01:21:36Z at revision `50dbac567d2c5cc8e55e6c748a646be0025d9cfb (CLI 0.1.21)`: Starlette pattern fixture deployed on Ample (pip install into .ample/python from requirements.txt, then uvicorn from run.py reading PORT on the python-3.12 template); for this guide: a --release-command migration ran before activation and its marker was readable by the live app (migrated=release-ok). (expires 2027-03-20T01:21:36Z)

EXECUTION

## Execution binding

MCP tool `ample_deploy` (registry `mcp:ample_deploy`), schema hash `876465fce906da0c` observed 2026-09-22T00:31:22.774679+00:00 at revision `e6446ceea69b`. 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 Starlette (`GET /v1/catalog/nodes/stack%3Aframework-starlette` 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:starlette:schema-changes`. Revision r1.

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

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