# Data cache

Toucan offers robust data caching mechanisms to enhance performance and responsiveness. This documentation provides an in-depth overview of the data caching features implemented in both the frontend (user's browser level) and backend (Toucan server level).

## Frontend data caching

The frontend data caching takes place within the user's web browser. This cache ensures that once a data request is made by a browser during a "session", it will not be repeated until the user refresh the page or quit Toucan (and comeback to it).

This cache feature is enabled by default.

## Backend data caching

The backend data caching takes place within Toucan backend server.

### Slow query caching

This is designed to cache server-side queries made via connectors in live data. If a query is slow (exceeding a certain amount of time defined by the parameter TOUCAN\_QUERY\_CACHE\_MIN\_TIME), it is cached and will not be rerun if another client requires the same data.

The parameter `TOUCAN_QUERY_CACHE_MIN_TIME` is set as **1000 ms** by default.

**Cache lifetime**

The cache lifetime is equals by default to **10 minutes**.

The duration is configurable at the connector, and query levels (for some connectors), within the field "Slow queries' cache expiration time."

{% hint style="info" %}
**Amount of data limits**

The maximum total amount of data cached cannot exceed **2GB**. When exceeding this limit, the data are not cached anymore.

The maximum amount of data for a specific query cannot exceed **200MB**, otherwise the data is not cached.
{% endhint %}

## Data preparation (YouPrep) caching

There is a specific cache that is used when making data preparation with YouPrep. This cache is applied **only on Toucan execution engine**, and not when evolving within a NativeSQL context.

The first step within YouPrep (aka Source step) is always kept in cache, and then when any following step takes more than 3 sec to be completed, the result is also cached in order to ensure a fluid experience within YouPrep.

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Cache lifetime

The cache is deleted once dataset edition interface is closed.

{% hint style="success" %}
You knows now everything on data caching system.
{% endhint %}