Which approach is least effective for improving database query performance?

Increasing server resources is often considered the least effective approach for improving database query performance because it may provide only a temporary or marginal benefit compared to optimizing the actual queries or data access patterns. While adding more CPU power, memory, or storage may help some workloads, it does not address the underlying inefficiencies in how the database queries are structured or how data is accessed.

In contrast, rewriting queries for better efficiency can lead to substantial performance gains by optimizing how data is retrieved. Adding indexes is a well-known strategy for significantly speeding up data retrieval, particularly for large datasets, as it allows the database engine to find the necessary records more quickly. Caching frequently accessed data reduces the need to access the database for common queries, effectively enhancing performance and reducing load.

Therefore, while resource enhancement can be part of a broader strategy, it is more beneficial to focus on optimizing queries, indexing, and utilizing caching mechanisms to achieve substantial improvements in database performance.