Techniques for detection over-the-top piracy are described. In some embodiments, a piracy detection method is performed at a server by a piracy detector. The piracy detector obtains records associated with requests for access from a plurality of client devices. The piracy detector further distributes the records to a plurality of nodes according to distribution keys extracted from the records, where each of the plurality of nodes receives a respective set of records associated with a respective distribution key and generates a set of respective watch session records based on the respective set of records. The piracy detector also generates watch session records associated with the distribution keys by aggregating the respective watch session records from the plurality of nodes. The piracy detector additionally identifies one or more pirated client devices among the plurality of client devices based on clusters established from the watch session records.