Dynamic

Only the sum aggregation type is compatible with the dynamic charge model. If you have a different use case, please reach out to the Lago team for assistance.

Select the dynamic charge model if you calculate the price manually or if prices fluctuate during a billing period (e.g., for SMS APIs, AI models, etc.), and you want to apply a specific total amount per event using the property precise_total_amount_cents.

Let’s take the example of our AI company. You may want to charge a custom price per event. Consider the following list of events:

Table view

Event	Metric	Unit	Total amount
Transaction 1	Dedicated Instance	7	$0.70
Transaction 2	Dedicated Instance	5	$0.55
Transaction 3	Dedicated Instance	10	$2.20

Events payload

List of events

{
  "events": [
    {
      "transaction_id": "transaction_1",
      "external_subscription_id": "123456789",
      "code": "dedicated_instance",
      "timestamp": 1728554400,
      "precise_total_amount_cents": "70", //event total amount
      "properties": {
        "unit": "7"
      }
    },
    {
      "transaction_id": "transaction_2",
      "external_subscription_id": "123456789",
      "code": "dedicated_instance",
      "timestamp": 1728558000,
      "precise_total_amount_cents": "55", //event total amount
      "properties": {
        "unit": "5"
      }
    },
    {
      "transaction_id": "transaction_3",
      "external_subscription_id": "123456789",
      "code": "dedicated_instance",
      "timestamp": 1728561600,
      "precise_total_amount_cents": "220", //event total amount
      "properties": {
        "unit": "10"
      }
    }
  ]
}

At the end of the period, the invoice will generate one fee of $3.45 (see example below).

Item	Unit	Unit price	Amount
Dedicated Instance	22	$0.156818	$3.45

To display more detailed information on fees, please refer to the custom invoice grouping or the pay in advance option.

Only the standard and dynamic charge models support the custom invoice grouping.