What metrics do you use to evaluate the efficiency and characteristics of database queries?

To assess the efficiency and characteristics of database queries, the following indicators are usually considered:

• Query execution time (Latency) — how long it takes to execute a query from start to finish.
• Resource consumption — load on CPU, memory, and disk during query execution.
• Number of returned rows — helps understand how optimized the query is and whether it returns unnecessary data.
• Query execution plan — analyzing the plan can reveal bottlenecks, such as full table scans instead of using indexes.
• Disk I/O operations — the fewer, the better, as disk operations are slower.
• Parallelism and locking — important for assessing the impact of the query on other operations.

Example: in PostgreSQL, you can use EXPLAIN ANALYZE to get a detailed plan and execution time of a query.

EXPLAIN ANALYZE SELECT * FROM users WHERE id = 123;

This helps understand how efficiently the query works and where it can be optimized.