page:recipes:mobile backend:flask:persistent state

Host mobile backend with Flask: Postgres-backed state

Deploy a mobile backend built with Flask 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 Flask: 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.

Prerequisites

• A Flask project that builds and starts with the documented commands (pip install into .ample/python from requirements.txt, then waitress from app.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.

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. Build and start: pip install into .ample/python from requirements.txt, then waitress from app.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.
   • Command: ample deploy . --name --public --start "python3 app.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.
   • Command: ample logs --kind build

Examples

• Flask pattern fixture: Multi-pattern Flask app whose durable job state module was checked live; the module is under tests/deploy-canaries/_pattern-modules. Source: tests/deploy-canaries/flask-patterns

Success Checks

• App responds on its public URL.
• Durable-job-state self-test: fetch /p/durable-job-state.

Limitations

• Verified on the python-3.12 template at s-1vcpu-1gb with the example fixture; other sizes, templates and Flask 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 x 1 = 5.0
  • Managed PostgreSQL database: s-1vcpu-1gb x 1 = 5.0
• Note: Always-on monthly price of the tested sizes; apps and databases auto-pause when idle.

Evidence Summary

• Canary run summary showing checks passed for durable-job-state and configuration-secrets.

Next Actions

• Browse the catalog index: GET /v1/catalog
• Search published recipes: POST /v1/catalog/search
• Prepare a deployment plan: POST /v1/catalog/plan
• Read existing authentication setup: GET /mcp/setup
• Browse Mobile backend: GET /v1/catalog/nodes/workload%3Amobile-backend
• Browse Flask: GET /v1/catalog/nodes/stack%3Aframework-flask
• Browse Durable job state: GET /v1/catalog/nodes/pattern%3Adurable-job-state
• Browse Deploy API: GET /v1/catalog/nodes/intent%3Adeploy-api