# Metrics Functions

When the simulation is running, you may want to store some performance parameters for analysis. Normally, you would need to create a separate backend application that could store such metrics, however with a very large-scale dataset, this could become difficult. IoTIFY provides a simple and easy-to-use time-series database for this purpose via our Metrics API.

To create any custom metric, use the following function.

```javascript
//requires a string key parameter and an optional value parameter as arguments
metric.add(key, ?value)

metric.add('latency', 55);
metric.add('count');          // Default value of 1 is taken
```

{% hint style="info" %}
If no value is passed to the function, a default value of 1 is taken.
{% endhint %}

These metrics can be visualized and aggregated in the **Metrics** tab on the Sidebar. Metrics will also be available via APIs. 


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