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+---
+title: Use EXPLAIN ANALYZE to Diagnose Slow Queries
+impact: LOW-MEDIUM
+impactDescription: Identify exact bottlenecks in query execution
+tags: explain, analyze, diagnostics, query-plan
+---
+
+## Use EXPLAIN ANALYZE to Diagnose Slow Queries
+
+EXPLAIN ANALYZE executes the query and shows actual timings, revealing the true performance bottlenecks.
+
+**Incorrect (guessing at performance issues):**
+
+```sql
+-- Query is slow, but why?
+select * from orders where customer_id = 123 and status = 'pending';
+-- "It must be missing an index" - but which one?
+```
+
+**Correct (use EXPLAIN ANALYZE):**
+
+```sql
+explain (analyze, buffers, format text)
+select * from orders where customer_id = 123 and status = 'pending';
+
+-- Output reveals the issue:
+-- Seq Scan on orders (cost=0.00..25000.00 rows=50 width=100) (actual time=0.015..450.123 rows=50 loops=1)
+--   Filter: ((customer_id = 123) AND (status = 'pending'::text))
+--   Rows Removed by Filter: 999950
+--   Buffers: shared hit=5000 read=15000
+-- Planning Time: 0.150 ms
+-- Execution Time: 450.500 ms
+```
+
+Key things to look for:
+
+```sql
+-- Seq Scan on large tables = missing index
+-- Rows Removed by Filter = poor selectivity or missing index
+-- Buffers: read >> hit = data not cached, needs more memory
+-- Nested Loop with high loops = consider different join strategy
+-- Sort Method: external merge = work_mem too low
+```
+
+Reference: [EXPLAIN](https://supabase.com/docs/guides/database/inspect)