A method of telemetry data collection, the method comprising: receiving a first plurality of telemetry data items each associated with a different software instance (120, 122, 124) and including a first value for a first performance measurement of the associated software instance; for each telemetry data item included in the first plurality of telemetry data items, generating a respective data object included in a first plurality of data objects, the generated data object providing values for a first set of attributes including: a plurality of context attributes each describing an operating environment in which the first value was measured, and a performance attribute measuring performance of a software instance, wherein a value for the performance attribute is determined based on at least the first value included in the telemetry data item; performing a machine-based selection of a first plurality of outlier data objects from the first plurality of data objects based on at least the first set of attributes; obtaining a first targeting rule specifying first selection conditions for at least two of the plurality of context attributes, the first selection conditions corresponding to a selected subset of the first plurality of outlier data objects; providing the first targeting rule to a plurality of telemetry sources (140, 144); and receiving a second plurality of telemetry data items each associated with a different telemetry source that satisfied the first selection conditions, and each including a second value for a second performance measurement of an associated software instance, wherein the first plurality of telemetry data items do not include values for the second performance measurement. receiving a first plurality of telemetry data items each associated with a different software instance (120, 122, 124) and including a first value for a first performance measurement of the associated software instance; for each telemetry data item included in the first plurality of telemetry data items, generating a respective data object included in a first plurality of data objects, the generated data object providing values for a first set of attributes including: a plurality of context attributes each describing an operating environment in which the first value was measured, and a performance attribute measuring performance of a software instance, wherein a value for the performance attribute is determined based on at least the first value included in the telemetry data item; a plurality of context attributes each describing an operating environment in which the first value was measured, and a performance attribute measuring performance of a software instance, wherein a value for the performance attribute is determined based on at least the first value included in the telemetry data item; performing a machine-based selection of a first plurality of outlier data objects from the first plurality of data objects based on at least the first set of attributes; obtaining a first targeting rule specifying first selection conditions for at least two of the plurality of context attributes, the first selection conditions corresponding to a selected subset of the first plurality of outlier data objects; providing the first targeting rule to a plurality of telemetry sources (140, 144); and receiving a second plurality of telemetry data items each associated with a different telemetry source that satisfied the first selection conditions, and each including a second value for a second performance measurement of an associated software instance, wherein the first plurality of telemetry data items do not include values for the second performance measurement.