Locking for performance
Locking is primarily designed to ensure that concurrent transactions can execute safely. However, locking is also a useful performance tool to optimize the performance of a particular transaction.
Consider, for example, a situation where we urgently require a complex report on the stock in the winestore that uses a slow SELECT statement with a GROUP BY, ORDER BY, and HAVING clause, and that joins together many tables. With other users running queries and using system resources, this query may run even slower. A solution is to use LOCK TABLES with the WRITE option to stop other users running queries or database updates, and to have exclusive access to the database for the query duration. This permits better optimization of the query processing by the DBMS, dedication of all the system resources to the query, and faster disk access.
The downside of locking for performance is the reduction in concurrent access to the database. Users may be inconvenienced by slow responses or timeouts from the web database application. Locking for performance should be used sparingly.