---
title: "Host rest api with Express: Postgres-backed state"
description: "Deploy an Express REST API whose durable state lives in a managed PostgreSQL 16 database."
canonical_url: "https://ample.computer/recipes/rest-api/express/persistent-state"
last_updated: "2026-09-19"
---

# Host rest api with Express: Postgres-backed state

Canonical URL: https://ample.computer/recipes/rest-api/express/persistent-state
Formats: [HTML](https://ample.computer/recipes/rest-api/express/persistent-state) | [Markdown](https://ample.computer/recipes/rest-api/express/persistent-state.md) | [JSON contract](https://api.ample.computer/v1/catalog/recipes/page%3Arecipes%3Arest-api%3Aexpress%3Apersistent-state)
Recipe ID: `page:recipes:rest-api:express:persistent-state` | Revision: `r1` | Catalog revision: `cat_f13ab9a494120b5e`

Status: release `published`, support `verified`, execution `ready`

## 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.

Path: [Agent hosting discovery](/discover/discovery) / [Applications and workloads](/discover/workload) / [Agents and backends](/discover/workload/agents-and-backends) / [REST API](/discover/workload/rest-api) / [Host rest api with Express: Postgres-backed state](/recipes/rest-api/express/persistent-state)

## Infrastructure requirements

- [Compute](/discover/primitive/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](/discover/primitive/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)


## Cost estimate

Estimated 10.00 USD per month (size prices from pricing.toml at build revision 515b7316fc6e5a81679407ae0c811146ceb2c5c7).
- 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 (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.

## Input schema

```json
{
  "additionalProperties": false,
  "properties": {
    "env": {
      "description": "Encrypted environment variables as KEY=value; secret values are never stored in ample.toml",
      "items": {
        "pattern": "^[A-Z][A-Z0-9_]*=.*$",
        "type": "string"
      },
      "maxItems": 50,
      "type": "array"
    },
    "name": {
      "description": "App name (lowercase, digits and dashes)",
      "maxLength": 63,
      "minLength": 1,
      "pattern": "^[a-z0-9-]+$",
      "type": "string"
    },
    "path": {
      "description": "Project directory to deploy, or one service name from ample.toml",
      "maxLength": 512,
      "minLength": 1,
      "type": "string"
    },
    "release_command": {
      "description": "One-off command run before the release goes live, for example a migration",
      "maxLength": 512,
      "minLength": 1,
      "type": "string"
    },
    "size": {
      "description": "VM size; omit to let Ample pick a runtime-safe size",
      "enum": [
        "s-1vcpu-256mb",
        "s-1vcpu-1gb",
        "s-1vcpu-2gb",
        "s-2vcpu-2gb",
        "s-2vcpu-4gb"
      ],
      "type": "string"
    }
  },
  "required": [
    "name",
    "path"
  ],
  "type": "object"
}
```

## Next actions

- Browse the catalog index (GET /v1/catalog on the api origin; auth: false, approval: false)
- Search published recipes by intent, stack and constraints (POST /v1/catalog/search on the api origin; auth: false, approval: false)
- Prepare a side-effect-free deployment plan for an authorized project (POST /v1/catalog/plan on the api origin; auth: true, approval: false)
- Read the existing agent authentication setup (GET /mcp/setup on the api origin; auth: false, approval: false)
- Browse REST API (GET /v1/catalog/nodes/workload%3Arest-api on the api origin; auth: false, approval: false)
- Browse Express (GET /v1/catalog/nodes/stack%3Aframework-express on the api origin; auth: false, approval: false)
- Browse Durable job state (GET /v1/catalog/nodes/pattern%3Adurable-job-state on the api origin; auth: false, approval: false)
- Browse Deploy API (GET /v1/catalog/nodes/intent%3Adeploy-api on the api origin; auth: false, approval: false)

Actions describe possible next steps. They are typed data, not commands, and grant no permission.