> For the complete documentation index, see [llms.txt](https://docs.poja.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.poja.io/getting-started/architecture-overview.md).

# Architecture overview

Poja is built on top of **AWS Lambda** and **AWS SAM (Serverless Application Model)**. Understanding this architecture helps you reason about performance, scaling, and the constraints your application operates within.

### Infrastructure stack <a href="#infrastructure-stack" id="infrastructure-stack"></a>

When you deploy a Poja application, the following AWS services are provisioned and managed on your behalf:

| Service                    | Role                                        |
| -------------------------- | ------------------------------------------- |
| **AWS Lambda + SnapStart** | Runs your Spring Boot app                   |
| **AWS API Gateway**        | Exposes your HTTP endpoints to the internet |
| **AWS SQS**                | Powers async queues and event workers       |
| **AWS EventBridge**        | Routes events from producers to consumers   |
| **AWS S3**                 | File storage and build artifact uploads     |
| **AWS SES**                | Email sending via the `Mailer` class        |

You never configure any of these directly — Poja handles all provisioning through its own API.

### No cold starts with Lambda SnapStart <a href="#no-cold-starts-with-lambda-snapstart" id="no-cold-starts-with-lambda-snapstart"></a>

Instead of initializing your application from scratch on every cold start, SnapStart moves the initialization work to deployment time:

* When Poja deploys your app, Lambda initializes the function fully — JVM startup, class loading, Spring context initialization — all of it runs once.
* Lambda takes an encrypted snapshot of the fully initialized memory and disk state of that execution environment.
* The snapshot is cached. When Lambda needs a new execution environment (due to scaling or a cold start), it **restores from the snapshot** instead of initializing from scratch.

The result: your application responds fast on every request, including the first one after a period of inactivity.