Why Apache Spark is often considered as slow?

The question about why Apache Spark is "slow" is one of the most often questions I'm hearing from junior engineers and peoples I'm mentoring. While that is partially true, it should be clarified. TLDR – OSS Spark is a multi-purpose engine that is designed to handle different kinds of workloads. Under the hood of Spark is using a data-centric code generation but also it has some vectorization as…