PostgreSQL query optimization can significantly improve database performance, and some techniques can boost performance by 100x or more. The `EXPLAIN ANALYZE` command provides detailed information about query execution time, helping to understand if specific indexes are used. Creating one index per unique query and using multiple columns in index can improve performance, but it's essential to consider the trade-off between storage space and query time. Column order in a multicolumn index is also crucial, with filters and joins requiring careful consideration of indexing strategies to achieve optimal results. By following these tips, developers can solve most performance bottlenecks in an 80/20 manner, leading to significant improvements in database performance.