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SELECT 
  `PF`.*, 
  `PFF`.`feature_type` 
FROM 
  `cscart_product_filters` AS `PF` 
  LEFT JOIN `cscart_product_features` AS `PFF` ON `PF`.`feature_id` = `PFF`.`feature_id` 
WHERE 
  1 
  AND `PF`.`filter_id` IN (737) 
  AND `PF`.`status` = 'A'

Query time 0.00040

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}