# Build brief — a focused alternative to Fly.io

> **Verdict:** Not faithfully · **Buildability:** 35/100 · **Category:** Hosting
> **Source:** https://www.canitbevibecoded.com/fly-io
> Independent editorial assessment from Can It Be Vibe Coded? Not affiliated with, endorsed by, or derived from Fly.io. Verify current pricing and capabilities before acting.

## Context

**Fly.io** — Deploy one container on a self-owned host and expose operational limits clearly. It currently costs Variable pricing.

A consolation build is possible, but the paid product's decisive value sits outside a solo rebuild. For Fly.io, deploy one container on a self-owned host and expose operational limits clearly. The hard boundary is global edge compute, anycast networking, orchestration, volumes, and platform operations, plus infrastructure scale, operations, and reliability.

This brief describes a focused, single-operator replacement for the part of Fly.io that is genuinely reproducible. It is deliberately narrower than the product it replaces, and it says so in writing. Build the useful core; do not pretend to have rebuilt the rest.

## What you are building

Deploy one container on a user-owned server, route domains, retain logs, perform backups, and expose operational limits clearly.

- Build a focused single-user workflow with real persistence, search, and export.
- A responsive interface with real empty, loading, success, and error states.

## Requirements

### Functional

- Linux server.
- Docker.
- Domain and DNS access.
- Backup destination.
- Basic systems administration.

### Non-functional

- Accessibility: semantic markup, labelled controls, visible focus, and reduced-motion support.
- Security: server-side secrets, validated input, and no credentials in the client bundle.
- Reliability: retries with backoff on external calls, and a clear failure state when a provider is down.
- Portability: the operator can export their data and leave without losing it.

## Implementation brief

Build a closest honest personal substitute for Fly.io in an empty repository.
Use Docker Compose, Caddy, PostgreSQL, Redis, and a small Go control plane; do not offer alternative stacks.
The core loop is: deploy one container on a user-owned server, route domains, retain logs, perform backups, and expose operational limits clearly.
Make the first run work locally with one documented command.
Store all user data locally by default and make export straightforward.
Put secrets in .env, ship .env.example, and never commit credentials.
Accept a Git repository or container image and one explicit Dockerfile-based build path.
Implement applications, environments, secrets, domains, health checks, and rolling container replacement.
Use Caddy for automatic TLS and route only to healthy local containers.
Capture bounded build and runtime logs and expose restart, rollback, and redeploy actions.
Back up PostgreSQL metadata and document backups for each deployed application's data volumes.
Add host metrics, disk alerts, update instructions, disaster recovery, and a prominent single-server warning.
Include clear empty, loading, success, and recoverable error states.
Add input validation, safe filenames, and graceful handling of unavailable APIs.
Write focused tests for the core transformation and one end-to-end happy path.
Create a README with setup, architecture, permissions, data location, and backup steps.
Do not add accounts, billing, telemetry, analytics, or a hosted control plane.
Do not claim to reproduce proprietary data, network liquidity, regulated access, or frontier infrastructure.
Deliberately leave out multi-region or serverless infrastructure.
Deliberately leave out managed data stores and global edge delivery.
Deliberately leave out DDoS response, compliance, and guaranteed uptime.
Finish by running the tests and listing the exact commands used.

## Delivery standard

- Inspect the repository first, then write a short implementation plan before writing code.
- Deliver the smallest complete end-to-end workflow first; every primary control must work against persisted data.
- Use real validation and storage; never substitute fake dashboards, decorative controls, hard-coded success states, or mock integrations.
- Include responsive layouts plus genuine empty, loading, success, validation, and failure states.
- Keep secrets server-side in environment variables, provide .env.example, and never commit credentials or user data.
- Add structured logs around every external call and return actionable errors without leaking sensitive details.
- Write unit tests for the core logic and one automated test of the main user journey.
- Finish with a README covering setup, architecture, data location, backups, tests, deployment, and known limitations.

## Acceptance criteria

- [ ] A clean install starts the app using only the README and .env.example.
- [ ] The primary journey works from first visit through saved result, reload, edit, export, and deletion where applicable.
- [ ] Invalid input, missing configuration, provider failure, and an empty database each have a usable state.
- [ ] The interface works at 390px and 1440px, is keyboard navigable, and shows visible focus on every control.
- [ ] Tests, type checking, linting, and a production build all pass with no ignored failures.
- [ ] No part of the interface implies a live integration, security guarantee, or scale capability that was not actually built and verified.

## Non-goals

Do not build these, and do not claim to have replaced them:

- Global edge compute, anycast networking, orchestration, volumes, and platform operations.
- Global edge network.
- Managed databases.
- Autoscaling.
- Reliability at the vendor's scale is an operations problem, not a prompt.

## What you still own after launch

- Run migrations, backups, restores, and dependency updates.
- Test the critical journey after every model, API, or hosting change.
- Monitor failures and fix the edge cases a first prompt will miss.

## Risk

**Operational risk.** The code is achievable; dependable data, integrations, and ongoing operations are the real cost.

Editorial confidence in this assessment: high. No independent one-shot implementation is linked yet.

## Prior art

Working open-source software you can read, fork, or borrow from before starting:

- [Coolify](https://github.com/coollabsio/coolify) — Active open-source self-hosting platform for applications, databases, and services

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Generated by [Can It Be Vibe Coded?](https://www.canitbevibecoded.com) · Full report: https://www.canitbevibecoded.com/fly-io