An example embodiment may involve a main database; a main memory; and one or more processors configured to: retrieve, by a data collector application, records from the main database, wherein the data collector application includes an embedded database; aggregate, by the data collector application, values in the records relating to a key performance indicator (KPI) to form partial KPI data stored in one or more blocks of the main memory; determine, by the data collector application, that utilization of the main memory exceeds a pre-defined threshold; in response to the utilization of the main memory exceeding the pre-defined threshold, write, by the data collector application, the partial KPI data to a row of the embedded database; and release, by the data collector application, the one or more blocks of the main memory used to store the partial KPI data.