Your Spark Cluster Is a Restaurant Kitchen at Rush Hour

The mental model that makes every bottleneck obvious

Most engineers can recite what a Spark cluster is made of. Driver, executors, cores, partitions, shuffle. They have the vocabulary cold.

Then a job that ran in four minutes yesterday takes forty today, same data, same code, and the vocabulary stops helping. They start changing settings at random. More memory. More nodes. Repartition to some number a blog…