Using redundant conditions as a method to unlock obfuscated indexes and improve performance in MySQL is an effective technique that can be used when working with the database. Obfuscating an index occurs when queries are written in such a way that they hide the indexed value from MySQL, preventing it from using the index effectively. However, adding redundant conditions to queries can sometimes unlock existing indexes by allowing MySQL to use them more efficiently. Redundant conditions are conditions that seem superfluous or not needed but can be added and removed without changing the results of a query. In some cases, domain-specific knowledge can be used to add redundant conditions that logically cannot change the result set, but may still allow MySQL to use the index effectively. By using redundant conditions, developers can improve performance in their queries and optimize their database's indexing strategy.