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

> Learn about Cube Core's production deployment architecture, including API instances, refresh workers, and Cube Store.

# Architecture

A typical production deployment of Cube Core includes several components
working together. This page describes the architecture and how each
component fits in.

## Components

As shown in the diagram below, a typical production deployment of Cube includes
the following components:

* One or multiple API instances
* A Refresh Worker
* A Cube Store cluster

<div style={{ textAlign: "center" }}>
  <img alt="Deployment Overview" src="https://ucarecdn.com/b4695d0a-46a9-4552-93f8-71309de51a43/" style={{ border: "none" }} width="100%" />
</div>

**API Instances** process incoming API requests and query either Cube Store for
pre-aggregated data or connected database(s) for raw data. The **Refresh
Worker** builds and refreshes pre-aggregations in the background. **Cube Store**
ingests pre-aggregations built by Refresh Worker and responds to queries from
API instances.

API instances and Refresh Workers can be configured via [environment
variables][ref-config-env] or the [`cube.js` configuration file][ref-config-js].
They also need access to the data model files. Cube Store clusters can be
configured via environment variables.

You can find an example Docker Compose configuration for a Cube deployment in
the platform-specific guide for \[Docker]\[ref-deploy-docker].

## API instances

API instances process incoming API requests and query either Cube Store for
pre-aggregated data or connected data sources for raw data. It is possible to
horizontally scale API instances and use a load balancer to balance incoming
requests between multiple API instances.

The [Cube Docker image][dh-cubejs] is used for API Instance.

API instances can be configured via environment variables or the `cube.js`
configuration file, and **must** have access to the data model files (as
specified by [`schema_path`][ref-conf-ref-schemapath].

## Refresh Worker

A Refresh Worker updates pre-aggregations and invalidates the in-memory cache in
the background. They also keep the refresh keys up-to-date for all data models
and pre-aggregations. Please note that the in-memory cache is just invalidated
but not populated by Refresh Worker. In-memory cache is populated lazily during
querying. On the other hand, pre-aggregations are eagerly populated and kept
up-to-date by Refresh Worker.

The [Cube Docker image][dh-cubejs] can be used for creating Refresh Workers; to
make the service act as a Refresh Worker, `CUBEJS_REFRESH_WORKER=true` should be
set in the environment variables.

## Cube Store

Cube Store is the purpose-built pre-aggregations storage for Cube.

Cube Store uses a distributed query engine architecture. In every Cube Store
cluster:

* a one or many [router nodes](#cube-store-cube-store-router) handle incoming
  connections, manages database metadata, builds query plans, and orchestrates
  their execution
* multiple [worker nodes](#cube-store-cube-store-worker) ingest warmed up data
  and execute queries in parallel
* a local or cloud-based blob storage keeps pre-aggregated data in columnar
  format

<div style={{ textAlign: "center" }}>
  <img alt="Cube Store Router with two Cube Store Workers" src="https://cubedev-blog-images.s3.us-east-2.amazonaws.com/db0e1aeb-3101-4280-b4a4-902e21bcd9a0.png" style={{ border: "none" }} width="100%" />
</div>

By default, Cube Store listens on the port `3030` for queries coming from Cube.
The port could be changed by setting `CUBESTORE_HTTP_PORT` environment variable.
In a case of using custom port, please make sure to change
[`CUBEJS_CUBESTORE_PORT`](/reference/configuration/environment-variables#cubejs_cubestore_port) environment variable for Cube API Instances and Refresh
Worker.

Both the router and worker use the [Cube Store Docker image][dh-cubestore]. The
following environment variables should be used to manage the roles:

| Environment Variable    | Specify on Router? | Specify on Worker? |
| ----------------------- | ------------------ | ------------------ |
| `CUBESTORE_SERVER_NAME` | ✅ Yes              | ✅ Yes              |
| `CUBESTORE_META_PORT`   | ✅ Yes              | —                  |
| `CUBESTORE_WORKERS`     | ✅ Yes              | ✅ Yes              |
| `CUBESTORE_WORKER_PORT` | —                  | ✅ Yes              |
| `CUBESTORE_META_ADDR`   | —                  | ✅ Yes              |

<Info>
  Looking for a deeper dive on Cube Store architecture? Check out
  [this presentation](https://docs.google.com/presentation/d/1oQ-koloag0UcL-bUHOpBXK4txpqiGl41rxhgDVrw7gw/)
  by our CTO, [Pavel][gh-pavel].
</Info>

### Cube Store Router

<div style={{ textAlign: "center" }}>
  <img alt="Cube Store Router with two Cube Store Workers" src="https://ucarecdn.com/bfc4f46a-09c2-4e2d-a8e8-8bb6177bb5ff/" style={{ border: "none" }} width="100%" />
</div>

The Router in a Cube Store cluster is responsible for receiving queries from
Cube, managing metadata for the Cube Store cluster, and query planning and
distribution for the Workers. It also [provides a MySQL-compatible
interface][ref-caching-inspect-sql] that can be used to query pre-aggregations
from Cube Store directly. Cube **only** communicates with the Router, and does
not interact with Workers directly.

[ref-caching-inspect-sql]: /docs/pre-aggregations/using-pre-aggregations#inspecting-pre-aggregations

### Cube Store Worker

<div style={{ textAlign: "center" }}>
  <img alt="Cube Store Router with two Cube Store Workers" src="https://ucarecdn.com/bedc67d5-b8ab-447f-8d7a-0176487e02a5/" style={{ border: "none" }} width="100%" />
</div>

Workers in a Cube Store cluster receive and execute subqueries from the Router,
and directly interact with the underlying distributed storage for insertions,
selections and pre-aggregation warmup. Workers **do not** interact with each
other directly, and instead rely on the Router to distribute queries and manage
any associated metadata.

### Scaling

Although Cube Store *can* be run in single-instance mode, this is often
unsuitable for production deployments. For high concurrency and data throughput,
we **strongly** recommend running Cube Store as a cluster of multiple instances
instead. Because the storage layer is decoupled from the query processing
engine, you can horizontally scale your Cube Store cluster for as much
concurrency as you require.

A sample Docker Compose stack setting Cube Store cluster up might look like:

```yaml theme={"dark"}
services:
  cubestore_router:
    image: cubejs/cubestore:latest
    environment:
      - CUBESTORE_WORKERS=cubestore_worker_1:10001,cubestore_worker_2:10002
      - CUBESTORE_REMOTE_DIR=/cube/data
      - CUBESTORE_META_PORT=9999
      - CUBESTORE_SERVER_NAME=cubestore_router:9999
    volumes:
      - .cubestore:/cube/data
    depends_on:
      - cubestore_worker_1
      - cubestore_worker_2

  cubestore_worker_1:
    image: cubejs/cubestore:latest
    environment:
      - CUBESTORE_WORKERS=cubestore_worker_1:10001,cubestore_worker_2:10002
      - CUBESTORE_SERVER_NAME=cubestore_worker_1:10001
      - CUBESTORE_WORKER_PORT=10001
      - CUBESTORE_REMOTE_DIR=/cube/data
      - CUBESTORE_META_ADDR=cubestore_router:9999
    volumes:
      - .cubestore:/cube/data

  cubestore_worker_2:
    image: cubejs/cubestore:latest
    environment:
      - CUBESTORE_WORKERS=cubestore_worker_1:10001,cubestore_worker_2:10002
      - CUBESTORE_SERVER_NAME=cubestore_worker_2:10002
      - CUBESTORE_WORKER_PORT=10002
      - CUBESTORE_REMOTE_DIR=/cube/data
      - CUBESTORE_META_ADDR=cubestore_router:9999
    volumes:
      - .cubestore:/cube/data
```

### Storage

Cube Store makes use of a separate storage layer for storing metadata as well as
for persisting pre-aggregations as Parquet files. Cube Store can use both AWS S3
and Google Cloud, or if desired, a local path on the server if all nodes of a
cluster run on a single machine.

A simplified example using AWS S3 might look like:

```yaml theme={"dark"}
services:
  cubestore_router:
    image: cubejs/cubestore:latest
    environment:
      - CUBESTORE_SERVER_NAME=cubestore_router:9999
      - CUBESTORE_META_PORT=9999
      - CUBESTORE_WORKERS=cubestore_worker_1:9001
      - CUBESTORE_S3_BUCKET=<BUCKET_NAME_IN_S3>
      - CUBESTORE_S3_REGION=<BUCKET_REGION_IN_S3>
      - CUBESTORE_AWS_ACCESS_KEY_ID=<AWS_ACCESS_KEY_ID>
      - CUBESTORE_AWS_SECRET_ACCESS_KEY=<AWS_SECRET_ACCESS_KEY>
  cubestore_worker_1:
    image: cubejs/cubestore:latest
    environment:
      - CUBESTORE_SERVER_NAME=cubestore_worker_1:9001
      - CUBESTORE_WORKER_PORT=9001
      - CUBESTORE_META_ADDR=cubestore_router:9999
      - CUBESTORE_WORKERS=cubestore_worker_1:9001
      - CUBESTORE_S3_BUCKET=<BUCKET_NAME_IN_S3>
      - CUBESTORE_S3_REGION=<BUCKET_REGION_IN_S3>
      - CUBESTORE_AWS_ACCESS_KEY_ID=<AWS_ACCESS_KEY_ID>
      - CUBESTORE_AWS_SECRET_ACCESS_KEY=<AWS_SECRET_ACCESS_KEY>
    depends_on:
      - cubestore_router
```

[dh-cubejs]: https://hub.docker.com/r/cubejs/cube

[dh-cubestore]: https://hub.docker.com/r/cubejs/cubestore

[ref-config-env]: /reference/configuration/environment-variables

[ref-config-js]: /reference/configuration/config

[ref-conf-ref-schemapath]: /reference/configuration/config#schema_path

[gh-pavel]: https://github.com/paveltiunov