# Host Mobile Backend with Starlette: Postgres-backed State

Deploy a mobile backend built with Starlette on Ample using the durable job state pattern. Compute runs the app in an isolated microVM behind a public HTTPS URL, a managed PostgreSQL 16 database is auto-provisioned and injected as DATABASE_URL. Verified on Starlette: a jobs table with a state and attempts counter, processing inside a row-locked transaction, and a second run that is a no-op (job=done attempts=1 idempotent=true). Not separately tested: your job types, payload schema and retry policy; treat the mobile backend-specific behavior as your application code.

## Representative Queries
- Host mobile backend with Starlette: Postgres-backed state
- Where can I host Mobile backend built with Starlette?
- I need a durable state schema and retry/recovery semantics implemented by application code.

## 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 Starlette project that builds and starts with the documented commands (pip install into .ample/python from requirements.txt, then uvicorn from run.py reading PORT on the python-3.12 template).  
- A PostgreSQL driver reading DATABASE_URL at runtime (auto-provisioned when omitted, or supplied with --env).  
- An Ample account token with servers:write, databases:read.

## Workflow Steps
1. **Build and start**  
   pip install into .ample/python from requirements.txt, then uvicorn from run.py reading PORT on the python-3.12 template. The server must bind 0.0.0.0 on PORT.

2. **Implement the pattern on PostgreSQL**  
   The fixture's module implements durable job state: a jobs table with a state and attempts counter, processing inside a row-locked transaction, and a second run that is a no-op (job=done attempts=1 idempotent=true). Copy the approach into your schema; keep migrations idempotent and run them with --release-command.

3. **Deploy**  
   Run the synchronous deploy once and read the result (exit 0 live, 1 failed, 2 blocked). Re-running with no change is a no-op.  
   `ample deploy . --name  --public --start "python3 run.py"`

4. **Verify**  
   Fetch the live URL and the pattern self-test route(s) (/p/durable-job-state) from the example; then run your own checks. On failure read `ample logs  --kind build` then `--kind runtime`.  
   `ample logs  --kind build`

## Examples
- **Starlette pattern fixture**  
  Multi-pattern Starlette app whose durable job state module was checked live; the module is under tests/deploy-canaries/_pattern-modules.

## Success Checks
1. app responds on its public URL  
   - Expected: ample canary starlette patterns

2. durable-job-state self-test  
   - Expected: job=done attempts=1 idempotent=true

## Limitations
- Verified on the python-3.12 template at s-1vcpu-1gb with the example fixture; other sizes, templates and Starlette major versions are not verified.
- The mobile backend itself (your job types, payload schema and retry policy) is application code and was not separately tested; the pattern checks are what was verified.
- 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 databases are placed together.

## Cost Estimate
- Currency: USD  
- Monthly Amount: 10.0  
- Components:  
  - App server (s-1vcpu-1gb): 5.0  
  - Managed PostgreSQL database (s-1vcpu-1gb): 5.0  
  - Note: Always-on monthly price of the tested sizes; apps and databases auto-pause when idle. Buckets are allocation-priced per quota and not included.

## Evidence Summary
1. **Canary run**  
   Starlette pattern fixture deployed on Ample; checks passed for durable-job-state and configuration-secrets.

2. **Canary run**  
   The same Starlette app deployed with a --release-command migration; the marker it created was readable after activation.

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### Last Verified At  
- 2026-09-21T01:21:36Z