  Many current applications have to perform data processing in a streaming
fashion. Doing so at a large scale requires a parallel system that must be
equipped to handle straggling workers and different kinds of failures. YT is
the main driver behind distributed systems at Yandex, home to its distributed
file system, lock service, key-value storage, and internal MapReduce platform.
We implement a new component of this system designed for performing streaming
MapReduce operations, utilizing different core YT solutions to achieve
fault-tolerance and exactly-once semantics while maintaining efficiency and low
write amplification factors.
