# Host rest api with FastAPI: Postgres-backed state

## Summary

Deploy a FastAPI REST API whose durable state lives in a managed PostgreSQL 16 database. With no DATABASE_URL supplied, Ample provisions the database and injects the connection string as an encrypted environment variable; the API stores rows with psycopg and serves them from a public HTTPS URL.

## 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

- requirements.txt with the framework, a server and psycopg
- A run.py that starts the server on PORT and 0.0.0.0 (pass --start "python3 run.py")
- Tables created by the app or by a --release-command migration, not assumed to exist
- An Ample account token with servers:write and 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. **Read DATABASE_URL at runtime.** Open the connection from the environment inside request handlers or a pool; a local .env is replaced by the managed database in production.
2. **Deploy.** Run the existing synchronous deploy once from the project directory and read the result. Exit 0 is live, 1 is failed, 2 is blocked on a required preflight action. Re-running with no change is a content-addressed no-op.
   
   ```
   ample deploy . --name <app-name> --public --format json --start "python3 run.py"
   ```
3. **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
   ```

## Tested examples

- **FastAPI + PostgreSQL canary** (tests/deploy-canaries/fastapi-postgres-api): REST API with an items table in an auto-provisioned managed PostgreSQL database.

## Success checks

- root route responds (`/` on the live URL, expect ample canary fastapi postgres api)
- database insert and count succeed (`/items` on the live URL, expect postgres=ok)

## Limitations

- Verified on the node-22 template at s-1vcpu-1gb; other templates and sizes are not verified by this recipe.
- Region, compliance attestations and request-duration limits are unknown and not claimed.
- Apps auto-pause when idle and wake on the next request; always-on is an operator setting, not a plan feature.
- Managed PostgreSQL 16 only; extensions, connection limits and backup or restore procedures are not verified.
- Apps and their managed databases are placed together; cross-node shared databases are unsupported.

## 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

Apps and managed databases auto-pause when idle; the estimate is the always-on monthly price of the tested sizes. Plan quotas and budgets apply.

## Verification evidence

- canary_run on 2026-09-20T01:42:25Z at revision `199ff1dfd52683832ae75d3f98b53a7a4bff7f96-dirty (CLI e3181f5)`: FastAPI REST API using psycopg with no DATABASE_URL supplied: Ample auto-provisioned a managed PostgreSQL 16 database and /items reported postgres=ok after a real insert and count. (expires 2027-03-19T01:42:25Z)
- canary_run on 2026-09-19T23:55:33Z at revision `1764076-tls-account-903d345`: Node app needing PostgreSQL with no DATABASE_URL: a managed database was auto-provisioned and /db reported postgres=ok. (expires 2027-03-18T23:55:33Z)

Last verified: 2026-09-20T01:42:25Z

## 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 `current`, required scopes: servers:write, databases:read.