Yet Another Resource Negotiator — the resource management layer in Hadoop that decides how much CPU and memory each job gets across the cluster. Before YARN, Hadoop could only run MapReduce; YARN lets any type of processing engine (Spark, Tez, etc.) share the same cluster by acting like an air-traffic controller that coordinates which applications run where and when.
A data engineering team runs Spark streaming jobs and batch MapReduce exports simultaneously on the same Hadoop cluster; YARN allocates resources between them so neither job starves the other.
These services offer managed Hadoop clusters that include YARN for resource management, enabling users to run various processing engines efficiently.