---
title: "How to host a REST API built with Express on Ample: worker execution and job state"
description: "Deploy a REST API built with Express as a public web service plus a dedicated worker process on Ample."
canonical_url: "https://ample.computer/recipes/rest-api/express/worker-state"
last_updated: "2026-11-05"
---

# How to host a REST API built with Express on Ample: worker execution and job state

Deploy a REST API built with Express as a public web service plus a dedicated worker process on Ample. `ample plan --write` discovers both services and their shared database and writes ample.toml; `ample up` reconciles the topology: a managed PostgreSQL 16 database, a public web microVM and a private worker microVM (kind worker, no public URL), both reading DATABASE_URL. Verified on Express: a separately deployed worker service (kind worker, no public URL) sharing a declared managed PostgreSQL database with the web service, consuming a jobs table with row locks and marking jobs done once (worker=done attempts=1). The REST API-specific behavior (your job payloads, retry policy and scheduling) is your application code on that verified basis.

## Infrastructure requirements

- [Compute](/discover/primitive/compute): verified (Apps run in isolated x86_64 Firecracker microVMs; sizes are the priced VM sizes.)
- [Postgres](/discover/primitive/postgres): verified (Managed PostgreSQL 16 with pgvector runs in its own microVM and is auto-provisioned when an app needs a database and no DATABASE_URL is supplied.)

## Prerequisites

- A repository with the web app and the worker as separate service directories (the fixture uses apps/web and apps/worker), each building and starting with the documented commands (npm install, npm run build --if-present, npm run start on the node-22 template; the worker starts with node worker (its own package.json start script) and binds no port)
- Both services read DATABASE_URL at runtime and share one jobs table; the worker claims rows with SELECT ... FOR UPDATE SKIP LOCKED and marks them done once
- An Ample account token with servers:write and databases:write (ample up creates the database)

## 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. **Plan the topology.** Run the planner once. It discovers the web and worker services, infers kind = "worker" for the process without a port, declares the database each service needs, and writes ample.toml. Exit 2 means it left questions in the manifest; answer them with --answer or by editing the file.

   ```
   ample plan --write .
   ```
2. **Share one database.** Keep a single [databases.main] with engine = "postgres", drop any per-service database the planner added, and set DATABASE_URL = { database = "main" } under both [services.web.env] and [services.worker.env].

   ```
   ample plan --offline .
   ```
3. **Apply.** Reconcile the whole manifest in dependency order: the database first, then both services. It is idempotent and never destructive; exit 0 means everything applied, 2 needs input, 1 a failed resource (independent siblings still proceed and re-running resumes).

   ```
   ample up .
   ```
4. **Verify.** Fetch the web service URL and its worker status route (/p/worker-queue/status in the example) and confirm the worker processed the enqueued job; on failure read the worker service's runtime logs.

   ```
   ample logs <deployment_id> --kind runtime
   ```

## Tested examples

- **Express web + worker fixture** (tests/deploy-canaries/express-worker): An Express web app (apps/web) and a worker process (apps/worker) sharing one managed PostgreSQL database; the queue module is under tests/deploy-canaries/_pattern-modules.

## Success checks

- web service responds on its public URL (`/` on the live URL, expect ample canary express patterns)
- worker consumed the enqueued job (`/p/worker-queue/status` on the live URL, expect worker=done attempts=1 result=processed-by-worker)


## Cost estimate

Estimated 15.00 USD per month (size prices from pricing.toml at build revision 4558e9477d094f5b47da324b98672824b61ba91b).
- web server x1 `s-1vcpu-1gb`: 5.00 USD
- worker server x1 `s-1vcpu-1gb`: 5.00 USD
- managed PostgreSQL database x1 `s-1vcpu-1gb`: 5.00 USD

Upper-bound monthly price of the tested sizes for the web service, the worker service and the database.

## Verification evidence

- canary_run on 2026-11-05T22:28:59Z at revision `da3e37255e5a`: Express web service plus a separate Express worker process deployed on Ample with `ample plan --write` then `ample up` (npm install, npm run build --if-present, npm run start on the node-22 template); the web service enqueued a job that the private worker service consumed from the shared managed PostgreSQL database. Pattern proof: a separately deployed worker service (kind worker, no public URL) sharing a declared managed PostgreSQL database with the web service, consuming a jobs table with row locks and marking jobs done once (worker=done attempts=1). (expires 2027-05-04T22:28:59Z)

Last verified: 2026-11-05T22:28:59Z


## Execution binding

MCP tool `ample_up` (registry `mcp:ample_up`), schema hash `29c90695d7a0dc2d` observed 2026-11-06T06:16:17.674112535+00:00 at revision `4558e9477d09`, binding state `current`, required scopes: servers:write, databases:write.

## Input schema

```json
{
  "additionalProperties": false,
  "properties": {
    "path": {
      "description": "Directory containing ample.toml (the whole topology is applied)",
      "maxLength": 512,
      "minLength": 1,
      "type": "string"
    },
    "wait_secs": {
      "description": "Maximum seconds to wait for each service deployment",
      "maximum": 3600,
      "minimum": 30,
      "type": "integer"
    }
  },
  "required": [
    "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 Dedicated worker process (GET /v1/catalog/nodes/pattern%3Adedicated-worker-process 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.

## About this recipe

Canonical URL: https://ample.computer/recipes/rest-api/express/worker-state
Formats: [HTML](https://ample.computer/recipes/rest-api/express/worker-state) | [Markdown](https://ample.computer/recipes/rest-api/express/worker-state.md) | [JSON contract](https://api.ample.computer/v1/catalog/recipes/page%3Arecipes%3Arest-api%3Aexpress%3Aworker-state)
Recipe ID: `page:recipes:rest-api:express:worker-state` | Revision: `r1` | Catalog revision: `cat_eac8c53f36410baa`
Status: verified; runs with one `ample deploy` call (support `verified`, execution `ready`)
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: worker execution and job state](/recipes/rest-api/express/worker-state)