Describe the methods of SQL query optimization you have applied. How did you reduce the execution time from 12-15 seconds?

To optimize SQL queries that initially took 12-15 seconds, I applied several approaches:

• Indexing: added indexes on columns involved in WHERE, JOIN, and ORDER BY clauses to speed up search and sorting.
• Rewriting queries: replaced subqueries with JOINs, simplified complex structures to allow the DBMS to better optimize the execution plan.
• Execution plan analysis: used EXPLAIN to identify bottlenecks and determine which operations took the most time.
• Limiting the selection: added LIMIT or filters to reduce the volume of data processed.
• Materialized views or caching: created intermediate tables with precomputed results for frequently repeated queries.

As a result of these actions, the execution time was reduced to 1-2 seconds, significantly improving system performance.