A computer-implemented method for detecting anomalies in a performance metric associated with computer application transactions in a distributed computing environment, comprising: - receiving, by a given server computer, a plurality of previous transaction events resulting from transactions executed in the distributed computing environment, where each transaction event is derived from a given transaction and each transaction event includes at least one classification parameter for the given transaction and a performance metric indicative of transaction execution; - grouping the plurality of previous transaction events into categories using the at least one classification parameter; and - segmenting the plurality of previous transaction events into observations windows, where each observation window is a fixed period of time within an overall observation period; characterized in that the method further comprises: - for each observation window, identifying one or more categories, where number of transaction events associated with an identified category in a given observation window exceeds a window threshold percent of all transaction events in the given observation window; - for each identified category, creating a window reference record in a data repository, where each window reference record includes a representative value for the performance metric during the given observation window; - for a given overall observation period, extracting categories having at least one window reference record with an observation window falling within the given overall observation period; - for each extracted category, determining a number of window reference records in the repository that fall within the given overall observation period; and - for each extracted category, constructing overall statistical reference data for the given overall observation period when the number of window reference records that fall within the given overall observation period exceeds an overall threshold percent of all observation windows comprising the overall observation period, where the overall statistical reference data includes a representative value for the performance metric during the overall observation period. - receiving, by a given server computer, a plurality of previous transaction events resulting from transactions executed in the distributed computing environment, where each transaction event is derived from a given transaction and each transaction event includes at least one classification parameter for the given transaction and a performance metric indicative of transaction execution; - grouping the plurality of previous transaction events into categories using the at least one classification parameter; and - segmenting the plurality of previous transaction events into observations windows, where each observation window is a fixed period of time within an overall observation period; - for each observation window, identifying one or more categories, where number of transaction events associated with an identified category in a given observation window exceeds a window threshold percent of all transaction events in the given observation window; - for each identified category, creating a window reference record in a data repository, where each window reference record includes a representative value for the performance metric during the given observation window; - for a given overall observation period, extracting categories having at least one window reference record with an observation window falling within the given overall observation period; - for each extracted category, determining a number of window reference records in the repository that fall within the given overall observation period; and - for each extracted category, constructing overall statistical reference data for the given overall observation period when the number of window reference records that fall within the given overall observation period exceeds an overall threshold percent of all observation windows comprising the overall observation period, where the overall statistical reference data includes a representative value for the performance metric during the overall observation period.