The count aggregation type is straightforward. It tallies the exact number of events received during a period.

COUNT calculation method

​
COUNT billable metric

Here is how you can create a count aggregation from the UI:
  1. Access the “Billable metrics” section via the side menu;
  2. Create a new billable metric;
  3. Define a name, a code and an optional description;
  4. Select “count” as the aggregation type;
  5. Apply dimension groups if any; and
  6. Click “Add billable metric”.
This billable metric is metered only, meaning it cannot be recurring, and the number of billing units resets to 0 at the end of each period.

​
Calculation example

Lago calculates the COUNT(events.code) for the two following events received. 
//Event received #1
{
    "transaction_id": "transaction_1",
    "external_customer_id": "1",
    "timestamp": "2022-03-16T00:00:00Z",
    "code": "api_requests",
    "properties": {}
}

//Event received #2
{
    "transaction_id": "transaction_2",
    "external_customer_id": "1",
    "timestamp": "2022-03-17T00:00:00Z",
    "code": "api_requests",
    "properties": {}
}
In that case, with this aggregation type, Lago simply counts the number events received, resulting in a billable value of 2 units.