Apache Spark 2.0 includes improvements that provide considerable speedups for CPU-intensive queries through techniques like code generation. Profiling tools like flame graphs can help analyze where CPU cycles are spent by visualizing stack traces. Flame graphs are useful for performance troubleshooting but have limitations. Testing Spark applications locally and through unit tests allows faster iteration compared to running on clusters and saves resources. It is also important to test with local approximations of distributed components like HDFS and Hive.