In the context of database performance, what is the 'data skew' phenomenon that occurs during a join operation on a distributed cluster?

Data skew is a performance bottleneck in distributed database systems where data is unevenly distributed across the nodes of a cluster during a join operation. In a distributed join, the database typically uses a shuffle process to redistribute rows from two tables so that rows with matching join keys end up on the same physical node. If one specific join ....