Livecount is an implementation of real-time counters that leverages the performance of memcache and task queues on Google AppEngine.
Building a solid analytics platform is often a combination of real-time and batch processing. Batch processing, with a tool like Hadoop, is great for digging into large amounts of past data and asking questions that cannot be anticipated. In contrast, when it is known ahead of time that certain aggregates will be required, the best solution is usually to count each event as it happens. Livecount makes it easier to address this second use-case.