> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cubby.pro/llms.txt
> Use this file to discover all available pages before exploring further.

# Core Concepts

> Understanding how Cubby works

# Core Concepts

Cubby is designed to be simple, but here are the key concepts to understand.

## Apps

An app is a deployed project. Each app gets:

* A unique URL: `<app-name>--<username>.cubby.pro`
* Cubby SSO in front of every request
* A SQLite database by default, or Neon Postgres on Builder/Pro when selected
* An isolated container
* TLS handled by the platform

## CUBBY.md

Every Cubby app should have a `CUBBY.md` file in its root. This file:

* Provides context to AI tools building your app
* Documents platform constraints
* Explains available APIs and patterns

When you run `cubby init`, this file is created automatically.

## Secrets

Environment variables are managed via `cubby secrets`. Secrets are:

* Encrypted at rest
* Injected at runtime
* Never exposed in logs

Common secrets: API keys, database URLs (auto-provided), third-party service credentials.

## Sharing

Apps can be shared with other Cubby users. Shared users:

* See the app in their dashboard
* Can access the app URL
* Cannot modify the app or its secrets

## Always Running

Your apps run continuously on Cubby. No cold starts, no wake-up delays. When a request comes in, your app responds immediately.

## Pricing Tiers

Cubby has four tiers: Free, Starter ($4.99/mo), Builder ($9.99/mo), and Pro (\$19.99/mo). Every new user gets a 30-day trial on their first deploy. See the [billing page](/platform/billing) for full details.