Adding a count and storing somewhere

We are looking for an efficient way to keep a count of the number of credits/ops used for customer billing purposes. We have a Teams account. However we have a single Scenario that runs for all our customer systems (rather than each customer having their own cloned Scenario). The challenge with this solution is that its not so easy to calculate the number of credits used per customer.

So what I’m currently thinking is adding a Data Store at the end of the Scenario which adds ‘1’ to a count based on one of the variables that is being passed within the Scenario. Basically the scenario runs from a make custom webhook. part of the data structure contains which customer is triggering the scenario. so we can easily count this but where best to store this information? can we use a data store to keep the list of customer IDs (about 100 customers) and somehow update a count field against each? or is this an expensive way to achieve this?

Thanks in advance!