# Configure an external in-memory cache

{% hint style="danger" %}
**This documentation is for the CARTO Self-Hosted Legacy Version**. Use only if you've installed this specific version. Explore our latest documentation for updated features.
{% endhint %}

CARTO Self-Hosted requires Redis (version 6 or above) to work. This Redis instance does not need persistence, as it is used solely as a cache.

Both [**Single VM deployment**](https://docs.carto.com/overview#single-vm-deployment-docker-compose) and [**Orchestrated container deployment**](https://docs.carto.com/overview#orchestrated-container-deployment-kubernetes) come already with an internal Redis deployment, but they lack any backups, autoscaling, or monitoring. Cloud vendors already offer Redis deployments at scale as a service:

* [Google Memorystore for Redis](https://cloud.google.com/memorystore).
* [Amazon ElastiCache for Redis](https://aws.amazon.com/elasticache/redis/).
* [Azure Cache for Redis](https://azure.microsoft.com/en-us/products/cache).

In this section, you will see how to configure the Self-hosted to use an external Redis provided by your cloud vendor.

## Single VM deployments (Docker Compose)

### Configuration

1. Comment the local Redis configuration:

   ```
   # Configuration for using a local redis, instead of a external one (comment when external redis)
   - LOCAL_REDIS_SCALE=1
   - REDIS_HOST=redis
   - REDIS_PORT=6379
   - REDIS_TLS_ENABLED=false
   + # LOCAL_REDIS_SCALE=1
   + # REDIS_HOST=redis
   + # REDIS_PORT=6379
   + # REDIS_TLS_ENABLED=false
   ```
2. Uncomment the external Redis configuration:

   ```
   # Your custom configuration for a external redis (comment when local redis)
   - # LOCAL_REDIS_SCALE=0
   - # REDIS_HOST=<FILL_ME>
   - # REDIS_PORT=<FILL_ME>
   - # REDIS_PASSWORD=<FILL_ME>
   - # REDIS_TLS_ENABLED=true
   # Only applies if Redis TLS certificate it's self signed, read the documentation
   # REDIS_TLS_CA=<FILL_ME>
   + LOCAL_REDIS_SCALE=0
   + REDIS_HOST=<FILL_ME>
   + REDIS_PORT=<FILL_ME>
   + REDIS_PASSWORD=<FILL_ME>
   + REDIS_TLS_ENABLED=true
   ```
3. Replace the `<FILL_ME>` placeholders with the right values.

### Configure TLS

By default, CARTO will try to connect to your Redis without TLS, in case you want to connect via TLS, you can configure it via `REDIS_TLS_ENABLED` env vars in the <mark style="color:orange;">customer.env</mark> file.

```
REDIS_TLS_ENABLED=true
```

> ⚠️ In case you are connecting to a Redis instance where the TLS certificate is self signed or from a custom CA you will need to configure the `REDIS_TLS_CA` variable

1. Copy your CA `.crt` file inside the `certs` folder. Rename the CA `.crt` file to `redis-tls-ca.crt`.
2. Uncomment the `REDIS_TLS_CA` env var in the <mark style="color:orange;">customer.env</mark> file.

   ```
   # Only applies if Redis TLS certificate it's selfsigned, read the documentation
   - # REDIS_TLS_CA=/usr/src/certs/redis-tls-ca.crt
   + REDIS_TLS_CA=/usr/src/certs/redis-tls-ca.crt
   ```