perf enhancement

README.md

@@ -172,6 +172,56 @@ func main() {
 }
 ```
 
+## Important: Query Builder Lifecycle
+
+⚠️ **Query builders are single-use and should not be reused:**
+
+```go
+// ❌ WRONG - Don't reuse query builders
+baseQuery := users.User.Select(users.ID, users.Email)
+baseQuery.Where(users.ID.Eq(1)).First(ctx, &id1, &email1)
+baseQuery.Where(users.Status.Eq(2)).First(ctx, &id2, &email2)
+// Second query has BOTH WHERE clauses - incorrect behavior!
+
+// ✅ CORRECT - Create new query each time
+users.User.Select(users.ID, users.Email).Where(users.ID.Eq(1)).First(ctx, &id1, &email1)
+users.User.Select(users.ID, users.Email).Where(users.Status.Eq(2)).First(ctx, &id2, &email2)
+```
+
+**Why?** Query builders are mutable and accumulate state. Each method call modifies the builder, so reusing the same builder causes conditions to stack up.
+
+### Thread Safety
+
+⚠️ **Query builders are NOT thread-safe** and must not be shared across goroutines:
+
+```go
+// ✅ CORRECT - Each goroutine creates its own query
+for i := 0; i < 10; i++ {
+    go func(id int) {
+        var email string
+        err := users.User.Select(users.Email).
+            Where(users.ID.Eq(id)).
+            First(ctx, &email)
+        // Process result...
+    }(i)
+}
+
+// ❌ WRONG - Sharing query builder across goroutines
+baseQuery := users.User.Select(users.Email)
+for i := 0; i < 10; i++ {
+    go func(id int) {
+        var email string
+        baseQuery.Where(users.ID.Eq(id)).First(ctx, &email)
+        // RACE CONDITION! Multiple goroutines modifying shared state
+    }(i)
+}
+```
+
+**Thread-Safe Components:**
+- ✅ Connection Pool - Safe for concurrent use
+- ✅ Table objects - Safe to share
+- ❌ Query builders - Create new instance per goroutine
+
 ## Usage Examples
 
 ### SELECT Queries