Identification of data candidates for data processing is performed in real time by a processor device in a distributed computing environment. Data candidates are sampled for performing a classification-based compression upon the data candidates. A heuristic is computed on a randomly selected data sample from the data candidate, the heuristic computed by, for each one of the data classes, calculating an expected number of characters to be in a data class, calculating an expected number of characters that will not belong to a predefined set of the data classes, and calculating an actual number of the characters for each of the data classes and the non-classifiable data.