Answer: Use SQL statements to analyze SPANNER_SYS.READ_STATS* tables., Use SQL statements to analyze SPANNER_SYS.QUERY_STATS* tables.

To address the issue of high read latency in a multi-regional Cloud Spanner instance, it's crucial to first identify the root cause of the performance degradation. Analyzing the SPANNER_SYS.READ_STATS* tables (Option C) can provide insights into read operations and help pinpoint inefficiencies or bottlenecks. Similarly, analyzing the SPANNER_SYS.QUERY_STATS* tables (Option D) can offer valuable information about query performance, including execution times and resource usage, which is essential for troubleshooting degraded performance. Changing the Cloud Spanner configuration from multi-region to single region (Option B) might reduce latency but could also impact the global availability of the application, making it a less optimal solution without further analysis. Using query parameters (Option A) can improve query performance but does not directly address the need to diagnose the root cause of the observed high read latency. Therefore, the most appropriate actions are to analyze the SPANNER_SYS.READ_STATS* and SPANNER_SYS.QUERY_STATS* tables to gather detailed performance metrics before making any configuration changes.

Author: LeetQuiz Editorial Team