DataYatriSpark, seen under the hood
Simulate

Simulation/Spark

Educational simulation
Spark

Join Simulator

Broadcast vs shuffle join — when the big table should stay put.

Watch the canvas:fact tabledimensionnetwork moveLive simulation
ordersfact · 8B rows2 TBregionsdimension · 12 rows20 MBSortMergeJoinboth sides must shuffle2TB20RExecutor 1idleRExecutor 2idleRExecutor 3idleCorrect — but 2 TB crossed the network for a 20 MB table4 GB × 3 executors = 12 GB of copies. Broadcast just became an OOM.
The cheapest join is the one where the big table never moves.