To prevent performance issues, where should filtering of query results be performed?

Filtering of query results should be performed in the database to prevent performance issues primarily because databases are optimized for handling large sets of data efficiently. When filtering occurs at the database level, only the relevant data is retrieved and sent over the network to the application server or client. This minimizes data transfer, reduces memory usage on the application server, and speeds up response times for end-users.

By executing filter operations within the database, you leverage the indexing capabilities and query optimization features that relational database management systems provide. These systems are designed to quickly process complex queries and perform filtering operations far more efficiently than an application server or client can.

In contrast, filtering in memory or on the application server can lead to increased resource consumption, as all data is loaded and processed despite potentially containing large amounts of irrelevant information. Client-side filtering can also degrade performance, particularly for users with limited bandwidth or less powerful devices, as more data will be transferred to them before any filtering can occur. Therefore, performing filtering operations in the database is the optimal practice to enhance overall application performance.