SELECT 
  cscart_discussion_posts.*, 
  cscart_discussion_messages.message, 
  cscart_discussion_rating.rating_value 
FROM 
  cscart_discussion_posts 
  LEFT JOIN cscart_discussion_messages ON cscart_discussion_messages.post_id = cscart_discussion_posts.post_id 
  LEFT JOIN cscart_discussion_rating ON cscart_discussion_rating.post_id = cscart_discussion_posts.post_id 
WHERE 
  cscart_discussion_posts.thread_id IN (145593) 
  AND cscart_discussion_posts.status = 'A' 
ORDER BY 
  cscart_discussion_posts.timestamp DESC 
LIMIT 
  0, 10

Query time 0.00052

JSON explain

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        "sort_key": "cscart_discussion_posts.`timestamp` desc",
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          "possible_keys": ["thread_id", "thread_id_2"],
          "key": "thread_id_2",
          "key_length": "6",
          "used_key_parts": ["thread_id", "status"],
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          "rows": 2,
          "filtered": 100,
          "index_condition": "cscart_discussion_posts.`status` = 'A'",
          "attached_condition": "cscart_discussion_posts.thread_id <=> 145593 and cscart_discussion_posts.`status` <=> 'A'"
        }
      }
    },
    "table": {
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      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["post_id"],
      "ref": ["cscart_migrate.cscart_discussion_posts.post_id"],
      "rows": 1,
      "filtered": 100
    },
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    }
  }
}

Result

post_id thread_id name timestamp user_id ip_address status email message rating_value
123791 145593 The Coffee Hub 1404956040 0 50.45.114.68 A This is the second location for us using these lights. We are so happy to get the look and style we wanted. Having the ability to basically customize the light with all your options make it our first stop at looking at lighting for our business. 5
123790 145593 Mike 1374414480 0 108.2.161.201 A The lamp is great looking and came relatively quickly. It is a bit bright as a house light as the interior of the shade is metalic and reflects a lot of light. When you view the shade from directly below (as we do with the house light when we leave the house), it gives off a bit more glare than we would like. But overall an excellent light and very sharp on our house. 4