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

# Aggregation examples

Imagine you are a Tracking API company (such as
[Segment.com](https://www.segment.com/)). For the same events received, the
result provided by the aggregation types proposed by Lago is completely
different. This result is used to charge your customers.

## Example of events received[](#example-of-events-received "Direct link to heading")

You decided to charge the `Tracked Pages`. **This is your Billable metric.**
Here are the 2 events sent by your backend to Lago, based on the consumption of
a customer:

```json Event received n°1 theme={"dark"}
{
  "transaction_id": "1111-1111-1111-1111",
  "external_customer_id": "1",
  "timestamp": "2022-03-16T00:00:00Z",
  "code": "tracked_pages",
  "properties": {
    "tracked_user_id": "1234-5678-9098-7654",
    "pageviews": 10
  }
}
```

```json Event received n°2 theme={"dark"}
{
  "transaction_id": "2222-2222-2222-2222",
  "external_customer_id": "1",
  "timestamp": "2022-03-17T00:00:00Z",
  "code": "tracked_pages",
  "properties": {
    "tracked_user_id": "1234-5678-9098-7654",
    "pageviews": 20
  }
}
```

Let's see below the differences between the aggregation types.

## Differences between the aggregation types[](#differences-between-the-aggregation-types "Direct link to heading")

| Aggregation      | Code                                                     | Units to be charged |
| ---------------- | -------------------------------------------------------- | ------------------- |
| **COUNT**        | `COUNT(tracked_pages)`                                   | 2                   |
| **SUM**          | `SUM(tracked_pages.properties.pageviews)`                | 30                  |
| **MAX**          | `MAX(tracked_pages.properties.pageviews)`                | 20                  |
| **COUNT UNIQUE** | `UNIQUE_COUNT(tracked_pages.properties.tracked_user_id)` | 1                   |

Based on the aggregation type you defined for your Billable metric
`Tracked Pages`, the result that is going to be charged to your customer is
completely different. Make sure to choose the right aggregation type for all
your Billable metrics. If you need help, don't hesitate to reach out to the Lago
Team!