Apply Database Schema Changes for Starlette

Schema changes for a Starlette app on Ample. 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.

Prerequisites

• 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

Resource Requirements

• Compute
• Postgres

Infrastructure Requirements

1. Compute
   Apps run in isolated x86_64 Firecracker microVMs that auto-pause when idle and wake on request; sizes are the priced VM sizes.

2. Postgres
   Managed PostgreSQL 16 runs in its own microVM and is auto-provisioned when an app needs a database and no DATABASE_URL is supplied.

Workflow Steps

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. Run migrations as the release command
   Ample runs the command before activation and fails the release if it exits non-zero; keep migrations idempotent.
   Command: ample deploy . --name <your-app-name> --public --start "python3 run.py" --release-command "python3 migrate.py"

3. Verify
   Fetch the live URL and /p/migrated on the example; on failure read the build and runtime logs.
   Command: ample logs <your-app-name> --kind build

Limitations

• Verified on the python-3.12 template at s-1vcpu-1gb; other sizes and Starlette major versions are not verified.
• Region, compliance attestations and request-duration limits are unknown and not claimed.
• Managed PostgreSQL 16 only; extensions, connection limits and backup or restore procedures are not verified.

Cost Estimate

• Currency: USD
• Monthly Amount: 10.0
• Basis: size prices from pricing.toml (loaded by the API) at build revision 1ac5595375130d45290090e82ed0f554ccd45405-dirty
• Components:
  • App server (size: s-1vcpu-1gb, quantity: 1.0, monthly amount: 5.0)
  • Managed PostgreSQL database (size: s-1vcpu-1gb, quantity: 1.0, monthly amount: 5.0)

Examples

Starlette pattern fixture

• Verified schema changes on Starlette.
• Source Reference: tests/deploy-canaries/starlette-patterns

Success Checks

1. App responds on its public URL (/)

   • Expected Response: ample canary starlette patterns

2. Migrated check from the example (/p/migrated)

   • Expected Response: see the pattern fixture checks

Evidence Summary

• Kind: canary_run
• Summary: 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).
• Observed At: 2026-09-21T01:21:36Z
• Implementation Revision: 50dbac567d2c5cc8e55e6c748a646be0025d9cfb-dirty (CLI 0.1.21)
• Expires At: 2027-03-20T01:21:36Z

Next Actions

1. Browse the catalog index

   • Method: GET
   • Relative Path: /v1/catalog

2. Search published recipes by intent, stack and constraints

   • Method: POST
   • Relative Path: /v1/catalog/search
   • Parameters:
     Body: { "limit": 5, "query": "Apply database schema changes for Starlette" }

3. Prepare a side-effect-free deployment plan for an authorized project

   • Method: POST
   • Relative Path: /v1/catalog/plan
   • Parameters:
     Body: { "inputs": {}, "projectId": "", "recipeId": "page:guides:starlette:schema-changes", "recipeRevision": "r1" }

4. Read the existing agent authentication setup

   • Method: GET
   • Relative Path: /mcp/setup

5. Browse Starlette

   • Method: GET
   • Relative Path: /v1/catalog/nodes/stack%3Aframework-starlette

6. Browse Configure deployment

   • Method: GET
   • Relative Path: /v1/catalog/nodes/intent%3Aconfigure-deployment

7. Browse Transactional workflows

   • Method: GET
   • Relative Path: /v1/catalog/nodes/pattern%3Atransactional-workflows