# Host rest api with Express: Postgres-backed state

## Summary

Deploy an Express 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 pg 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

- A package.json with a start script that listens on process.env.PORT (default 3000) and 0.0.0.0
- The pg driver (or another PostgreSQL client) reading process.env.DATABASE_URL
- 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: `node-22`
- runtime: `node`
- size: `s-1vcpu-1gb`
- install: `npm install`
- build: `npm run build --if-present`
- start: `npm run start`

## Steps

1. **Check the start script.** Ample runs npm install, npm run build --if-present and npm run start on the node-22 template. The server must bind 0.0.0.0 and read PORT.
2. **Read DATABASE_URL at runtime.** Create a pg Pool from process.env.DATABASE_URL. Do not hard-code localhost credentials; a local .env is replaced by the managed database in production.
3. **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
   ```
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
   ```

## Tested examples

- **Express + pg canary** (tests/deploy-canaries/express-postgres-api): Express API with POST /items and GET /items backed by an auto-provisioned managed PostgreSQL database.

## Success checks

- root route responds (`/` on the live URL, expect ample canary express 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 2026-09-19T23:55:33Z at revision `1764076-tls-account-903d345`: Express REST API using pg with no DATABASE_URL supplied: Ample auto-provisioned a managed PostgreSQL 16 database, injected the connection string, and /items reported postgres=ok after a real insert and count. (expires 2027-03-18T23:55:33Z)
- 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)
- 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)
- live_deployment on 2026-09-20T00:48:10Z at revision `199ff1dfd52683832ae75d3f98b53a7a4bff7f96-dirty (CLI e3181f5)`: Authorized end-to-end run through the catalog: public search, verified contract, side-effect-free plan (ready_for_approval with a signed plan token), operator approval, handoff to ample_deploy, live URL, and the recipe's success checks passed. (expires 2027-03-19T00:48:10Z)

Last verified: 2026-09-19T23:55:33Z

## 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.