# Host Mobile Backend with NestJS: Worker Execution and Job State

Deploy a mobile backend built with NestJS 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 NestJS: 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). Not separately tested: your job payloads, retry policy and scheduling; treat the mobile backend-specific behavior as your application code.

## Summary

- **Framework:** NestJS  
- **Workload:** Mobile Backend  
- **Release Status:** Published  
- **Support Status:** Verified  
- **Execution Status:** Ready  
- **Docs Only:** False

## Resource Requirements

- **Compute**  
- **Postgres**

### Infrastructure Requirements

1. **Compute**  
   - **Status:** Verified  
   - **Summary:** Apps run in isolated x86_64 Firecracker microVMs that auto-pause when idle and wake on request; sizes are the priced VM sizes.

2. **Postgres**  
   - **Status:** Verified  
   - **Summary:** 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 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, nest build (TypeScript) then node dist/main.js 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)

## Workflow 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.
   - **Command:** 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].
   - **Command:** 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).
   - **Command:** 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.
   - **Command:** ample logs  --kind runtime

## Limitations

- Verified on the node-22 template at s-1vcpu-1gb for both services with the example fixture; other sizes, templates and NestJS major versions are not verified.
- The mobile backend itself (your job payloads, retry policy and scheduling) is application code and was not separately tested; the worker-queue check is what was verified.
- The worker is a single long-running process supervised in its own microVM; there is no scheduler, cron or horizontal worker scaling in this recipe, and the check ran immediately after deploy so idle behavior of the worker VM is not verified.
- The worker service is private: it has no public URL and is reached only through the shared database; both services are placed with their database.
- Managed PostgreSQL 16 only; extensions, connection limits and backup or restore procedures are not verified; apps and their databases are placed together.
- Region, compliance attestations and request-duration limits are unknown and not claimed.

## Cost Estimate

- **Currency:** USD
- **Monthly Amount:** 15.0
- **Note:** Always-on monthly price of the tested sizes for the web service, the worker service and the database; apps auto-pause when idle.

### Components

- **Web Server**  
   - **Size:** s-1vcpu-1gb  
   - **Quantity:** 1.0  
   - **Monthly Amount:** 5.0

- **Worker Server**  
   - **Size:** s-1vcpu-1gb  
   - **Quantity:** 1.0  
   - **Monthly Amount:** 5.0

- **Managed PostgreSQL Database**  
   - **Size:** s-1vcpu-1gb  
   - **Quantity:** 1.0  
   - **Monthly Amount:** 5.0

## Success Checks

- **Web service responds on its public URL**  
   - **Kind:** http_get  
   - **Path:** /  
   - **Expect:** ample canary nestjs patterns

- **Worker consumed the enqueued job**  
   - **Kind:** http_get  
   - **Path:** /p/worker-queue/status  
   - **Expect:** worker=done attempts=1 result=processed-by-worker

## Examples

- **NestJS Web + Worker Fixture**  
   - **Description:** A NestJS 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.  
   - **Source Reference:** tests/deploy-canaries/nestjs-worker

## Evidence Summary

- **Kind:** canary_run  
- **Summary:** NestJS web service plus a separate NestJS worker process deployed on Ample with `ample plan --write` then `ample up` (npm install, nest build (TypeScript) then node dist/main.js 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).
- **Observed At:** 2026-09-20T03:56:46Z  
- **Implementation Revision:** 03b6402b1b3e19178985f08ea4033804521d85d4-dirty (CLI b75e104)  
- **Expires At:** 2027-03-19T03:56:46Z

## Next Actions

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- **Action ID:** browse:workload:mobile-backend  
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