## Host mobile backend with Starlette: worker execution and job state

### Summary
Deploy a mobile backend built with Starlette 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 Starlette: 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.

### Representative Queries
- Host mobile backend with Starlette: worker execution and job state
- Where can I host Mobile backend built with Starlette?
- I need a separately runnable worker, durable job records and idempotent retries; not a managed queue.

### Resource Requirements
- **Compute:** Apps run in isolated x86_64 Firecracker microVMs that auto-pause when idle and wake on request; sizes are the priced VM sizes.
- **Postgres:** Managed PostgreSQL 16 runs in its own microVM and is auto-provisioned when an app needs a database and no DATABASE_URL is supplied.

### 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]. Python services also need an explicit start command in the manifest (the fixture sets start for both services).  
   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`

### Examples
- **Starlette web + worker fixture**: A Starlette 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.

### Limitations
- Verified on the python-3.12 template at s-1vcpu-1gb for both services with the example fixture; other sizes, templates and Starlette 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 is a single long-running process supervised in its own microVM; there is no scheduler, cron or horizontal worker scaling in this recipe.

### Cost Estimate
- **Currency:** USD  
  **Monthly Amount:** 15.0  
  **Components:**  
  - Web server size: s-1vcpu-1gb, quantity: 1.0, monthlyAmount: 5.0
  - Worker server size: s-1vcpu-1gb, quantity: 1.0, monthlyAmount: 5.0
  - Managed PostgreSQL database size: s-1vcpu-1gb, quantity: 1.0, monthlyAmount: 5.0
  
  Note: Always-on monthly price of the tested sizes for the web service, the worker service and the database; apps auto-pause when idle.

### Evidence Summary
- **Summary**: Starlette web service plus a separate Python worker process deployed on Ample with `ample plan --write` then `ample up`. The web service enqueued a job that the private worker service consumed from the shared managed PostgreSQL database.  
  **Implemented at**: 2026-09-20T03:56:46Z