In the realm of database management, query optimizers play a crucial role in enhancing performance by minimizing resource usage such as memory, CPU, and disk I/O. Couchbase 6.5 introduced a cost-based optimizer (CBO) for its N1QL query service, which marks a significant advancement over traditional rule-based optimizers. This innovation is akin to using a dynamic route optimizer in navigation apps, offering significant improvements in executing complex queries efficiently by employing statistical data for decision-making rather than static rules. CBOs are particularly adept at handling the flexibility and complexity inherent in SQL and NoSQL systems, significantly impacting system throughput and the ability to meet service level agreements (SLAs). They achieve this by rewriting queries, selecting optimal access paths, determining join orders and types, and creating execution trees, ultimately ensuring that queries run with maximum efficiency. The introduction of CBOs in NoSQL databases like Couchbase highlights the growing importance of statistical optimization to handle real-world workloads effectively, emphasizing the necessity for enterprises to prioritize databases with robust optimizers.