> ## Documentation Index
> Fetch the complete documentation index at: https://www.aptible.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.
# Apps
## What is an Aptible App?
An Aptible App is a containerized web application. Aptible Apps have the following compatibility requirements:
* Apps run on Linux in Docker containers
* Apps only receive traffic over HTTP or TCP
Apps do not have persistent storage by default. To store your data with persistence, we recommend using a [Database](/docs/core-concepts/managed-databases/overview) or third-party storage solution, such as [AWS S3](/docs/how-to-guides/app-guides/use-s3-to-accept-file-uploads). For workloads that need a small amount of durable local state, you can attach a [Persistent Disk](/docs/core-concepts/apps/persistent-disks) to a single-container App service.
Like [Aptible's general architecture](/docs/core-concepts/architecture/overview), Apps run on EC2 instances under the hood, which is why containers can be distributed across separate Availability Zones for scaling and high availability, covered below.
Apps are made up of three components:
* **[An Image](/docs/core-concepts/apps/deploying-apps/image/overview):** Deploy directly from a Docker image, or push your code to Aptible with `git push` and the platform will build a Docker image for you.
* **[Services](/docs/core-concepts/apps/deploying-apps/services):** Services define how many containers Aptible will start for your app, what command they will run, and their Memory and CPU Limits. A single App can define multiple Services for different roles, such as `web`, `worker`, `cmd`, or `cron`, each running and scaling independently.
* **[Configuration](/docs/core-concepts/apps/deploying-apps/configuration) (optional):** The configuration is a set of keys and values securely passed to the containers as environment variables. For example - secrets are passed as configurations.
## Explore Starter Templates
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## Deployments
Aptible's Apps are designed for easy deployment and simplified management for developers. You can deploy code via [Git](/docs/core-concepts/apps/deploying-apps/image/deploying-with-git/overview), [Docker Image](/docs/core-concepts/apps/deploying-apps/image/deploying-with-docker-image/overview), and [CI/CD integration](/docs/how-to-guides/app-guides/how-to-deploy-aptible-ci-cd).
The process is similar regardless of method:
* You define your [Services](/docs/core-concepts/apps/deploying-apps/services) and [Configuration](/docs/core-concepts/apps/deploying-apps/configuration) (such as environment variables)
* Aptible provisions the underlying infrastructure securely and reliably
### Rollbacks
When things go wrong with deployments, Aptible makes it easy to restore your App to a good state:
* **[Automatic Rollbacks](/docs/core-concepts/architecture/operations#operation-rollbacks)**: When an infrastructure failure occurs, Aptible automatically restores your App to its last known good state.
* **[Instant Rollbacks](/docs/core-concepts/apps/deploying-apps/releases/rollbacks)**: Roll back to any previous Release on demand right from the Aptible Dashboard, restoring its exact container image without a new deploy.
### Zero-Downtime Deployments
Services with an [HTTP(S) Endpoint](/docs/core-concepts/apps/connecting-to-apps/app-endpoints/https-endpoints/overview#zero-downtime-deployment) deploy with zero downtime by default: new containers start accepting traffic before the old ones shut down. Services without an Endpoint can opt into the same cutover behavior; see [Releases](/docs/core-concepts/apps/deploying-apps/releases/overview) for how to enable it and for the health check requirements.
Services with an attached [Persistent Disk](/docs/core-concepts/apps/persistent-disks) can't deploy with zero downtime. The disk only mounts into one container at a time, so these deploys briefly stop the existing container before starting the new one.
### High Availability
Scale any App to [two or more containers](/docs/core-concepts/scaling/app-scaling#high-availability-apps), and Aptible automatically deploys it in a high-availability configuration: containers are distributed across separate AWS Availability Zones and deployed with zero downtime. There's no extra setup, HA comes standard the moment you cross that container count.
Services with an attached [Persistent Disk](/docs/core-concepts/apps/persistent-disks) are an exception: they run on a single container and incur a brief interruption on every deploy.
## Scaling
### Scale on Demand
Scale on demand by setting your [container count](/docs/core-concepts/scaling/app-scaling#horizontal-scaling), and adjust CPU/RAM by selecting a [Container Profile](/docs/core-concepts/scaling/container-profiles) to change the ratio. Aptible offers three Container Profiles: General Purpose, CPU-Optimized, and Memory Optimized.
Aptible also provides [in-app recommendations](/docs/core-concepts/scaling/container-efficiency-recommendations) for scaling, which flag when a Service is under- or over-provisioned and suggest the most optimal Container Profile and size.
### Advanced Autoscaling
Aptible also supports advanced autoscaling:
* [Horizontal autoscaling](/docs/core-concepts/scaling/app-scaling#horizontal-autoscaling) adds and removes containers automatically as demand changes, or on a schedule.
* [Vertical autoscaling](/docs/core-concepts/scaling/app-scaling#vertical-autoscaling) adjusts a container's CPU/RAM without you having to resize it manually.
## Connectivity
### Public/Private Access
Configure your App's Endpoint for public or private access. A [Public URL](/docs/core-concepts/apps/connecting-to-apps/app-endpoints/overview) exposes your App to the internet, with traffic automatically load-balanced across all containers for the service. You can optionally add an [IP allowlist](/docs/core-concepts/apps/connecting-to-apps/app-endpoints/ip-filtering) to restrict which clients are allowed to connect. For private access, expose an [Internal Endpoint](/docs/core-concepts/apps/connecting-to-apps/app-endpoints/overview#endpoint-placement) to your [Stack](/docs/core-concepts/architecture/stacks)'s internal network instead, for cases where only other services on your Stack should reach the App.
## Ephemeral SSH Sessions
Create an [Ephemeral SSH Session](/docs/core-concepts/apps/connecting-to-apps/ssh-sessions) configured identically to your App containers. Ephemeral SSH Sessions are great for debugging, one-off scripts, and running ad-hoc jobs, without needing to modify a running Service just to get a shell.
## Learn more using Apps on Aptible
Learn to deploy your code into Apps with an image, Services, and Configuration
Learn to expose your App to the internet with Endpoints and connect with ephemeral SSH sessions
Learn to scale, restart, rename, restart, and delete your Apps