database connection.md

Connect Postgres for Phoenix

Summary

Database connection for a Phoenix app on Ample. Verified on Phoenix: a managed PostgreSQL database auto-provisioned and injected as DATABASE_URL, with real queries succeeding at request time (records=ok). Build and start: mix deps.get, MIX_ENV=prod mix compile and mix release in the builder, then the release bin script with PHX_SERVER=true on the elixir-1.18 template; PORT, DATABASE_URL and SECRET_KEY_BASE read in config/runtime.exs.

Infrastructure requirements

Compute: verified (Apps run in isolated x86_64 Firecracker microVMs that auto-pause when idle and wake on request; sizes are the priced VM sizes.)
Postgres: verified (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 Phoenix project (mix deps.get, MIX_ENV=prod mix compile and mix release in the builder, then the release bin script with PHX_SERVER=true on the elixir-1.18 template; PORT, DATABASE_URL and SECRET_KEY_BASE read in config/runtime.exs)
A PostgreSQL driver reading DATABASE_URL at runtime
An Ample account token with servers:write, databases:read

Exact tested configuration

template: elixir-1.18
runtime: elixir
size: s-1vcpu-1gb
install: mix local.hex --force && mix local.rebar --force && MIX_ENV=prod mix deps.get --only prod
build: MIX_ENV=prod mix compile && MIX_ENV=prod mix release --overwrite
start: PHX_SERVER=true _build/prod/rel/$(ls _build/prod/rel | head -n 1)/bin/$(ls _build/prod/rel | head -n 1) start

Steps

Build and start. mix deps.get, MIX_ENV=prod mix compile and mix release in the builder, then the release bin script with PHX_SERVER=true on the elixir-1.18 template; PORT, DATABASE_URL and SECRET_KEY_BASE read in config/runtime.exs; the server must bind 0.0.0.0 on PORT.
Read DATABASE_URL at runtime. Open connections from the environment inside handlers or a pool; omit DATABASE_URL to auto-provision a managed database or pass --env DATABASE_URL=... for an existing one.
Verify. Fetch the live URL and /p/relational-records on the example; on failure read the build and runtime logs.
```
ample logs <deployment_id> --kind build
```

Tested examples

Phoenix pattern fixture (tests/deploy-canaries/phoenix-patterns): Verified database connection on Phoenix.

Success checks

app responds on its public URL (/ on the live URL, expect ample canary phoenix patterns)
relational-records check from the example (/p/relational-records on the live URL, expect see the pattern fixture checks)

Limitations

Verified on the elixir-1.18 template at s-1vcpu-1gb; other sizes and Phoenix major versions are not verified.
Region, compliance attestations and request-duration limits are unknown and not claimed.
Managed PostgreSQL 16 only; extensions, connection limits and backup or restore procedures are not verified.

Cost estimate

Estimated 10.00 USD per month (size prices from pricing.toml at build revision a1b8c38919e59cd035ebabaced73cf84ece24371).

app server x1 s-1vcpu-1gb: 5.00 USD
managed PostgreSQL database x1 s-1vcpu-1gb: 5.00 USD

Always-on monthly price of the tested sizes; apps auto-pause when idle. Buckets are allocation-priced per quota and not included.

Verification evidence

canary_run on 2026-09-20T23:45:31Z at revision 4d1511e574302f3904b75088bd4048a0975218b3-dirty (CLI 0.1.21): Phoenix pattern fixture deployed on Ample (mix deps.get, MIX_ENV=prod mix compile and mix release in the builder, then the release bin script with PHX_SERVER=true on the elixir-1.18 template; PORT, DATABASE_URL and SECRET_KEY_BASE read in config/runtime.exs); for this guide: a managed PostgreSQL database auto-provisioned and injected as DATABASE_URL, with real queries succeeding at request time (records=ok). (expires 2027-03-19T23:45:31Z)

Last verified: 2026-09-20T23:45:31Z

Execution binding

MCP tool ample_deploy (registry mcp:ample_deploy), schema hash 876465fce906da0c observed 2026-09-21T03:19:59.461917+00:00 at revision 49962bcade4f, binding state current, required scopes: servers:write, databases:read.