Loading data from an external API for a calculation

 # preparation module
  Ash.Query.before_transaction(query, fn query ->
    api_data = make_external_api_call()
    Ash.Query.put_context(query, :external_api_data, api_data)
  end)
 
  # calculation module
  def calculate(records, _opts, context) do
    api_data = context.source_context[:external_api_data]
    Enum.map(records, fn record -> 
       # get apppropriate field from api_data
       ... 
    end)
  end