Have you worked with Execution Plan? What metrics do you look at and how do you decide on indexes?

The Execution Plan shows how the DBMS executes a query and helps optimize it.

Key indicators I pay attention to:

• Types of operations (Seq Scan, Index Scan, Nested Loop, etc.) — sequential scans are usually slower than index scans.
• The number of rows processed at each stage — helps identify bottlenecks.
• Cost — an estimate of the resources needed for execution.

I decide on index solutions if I see:

• Frequent Seq Scans on large tables where an index on filterable or sortable fields can be added.
• Unused indexes — they can be removed to save space and speed up inserts.

Example: if a query frequently filters by the "user_id" column and the Execution Plan shows Seq Scan, I add an index:

CREATE INDEX idx_user_id ON table_name(user_id);

Then I check if the Execution Plan has changed and the query now uses an Index Scan.