Apply database schema changes for Starlette

Summary

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.

Infrastructure requirements

• Compute: verified (Apps run in isolated x86_64 Firecracker microVMs that auto-pause when idle and wake on request; sizes are the priced VM sizes.)
• Postgres: 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

• 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

Exact tested configuration

• template: python-3.12
• runtime: python
• size: s-1vcpu-1gb
• install: python3 -m pip install --target .ample/python -r requirements.txt
• start: PYTHONPATH=.ample/python:${PYTHONPATH:-} python3 run.py

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.

   ample deploy . --name <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.

   ample logs <deployment_id> --kind build
   

Tested examples

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

Success checks

• 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)

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

Estimated 10.00 USD per month (size prices from pricing.toml at build revision a1b8c38919e59cd035ebabaced73cf84ece24371).

• app server x1 s-1vcpu-1gb: 5.00 USD
• managed PostgreSQL database x1 s-1vcpu-1gb: 5.00 USD

Always-on monthly price of the tested sizes; apps auto-pause when idle. Buckets are allocation-priced per quota and not included.

Verification evidence

• canary_run on 2026-09-21T01:21:36Z at revision 50dbac567d2c5cc8e55e6c748a646be0025d9cfb-dirty (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)

Last verified: 2026-09-21T01:21:36Z

Execution binding

MCP tool ample_deploy (registry mcp:ample_deploy), schema hash 876465fce906da0c observed 2026-09-21T03:19:59.461917+00:00 at revision 49962bcade4f, binding state current, required scopes: servers:write, databases:read.