SELECT 
  discussion_posts.*, 
  discussion_messages.message, 
  discussion_rating.rating_value 
FROM 
  discussion_posts 
  LEFT JOIN discussion_messages ON discussion_messages.post_id = discussion_posts.post_id 
  LEFT JOIN discussion_rating ON discussion_rating.post_id = discussion_posts.post_id 
WHERE 
  discussion_posts.thread_id = 393 
  AND discussion_posts.status = 'A' 
ORDER BY 
  discussion_posts.timestamp DESC 
LIMIT 
  0, 10

Query time 0.00127

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "1.32"
    },
    "ordering_operation": {
      "using_filesort": true,
      "nested_loop": [
        {
          "table": {
            "table_name": "discussion_posts",
            "access_type": "ref",
            "possible_keys": [
              "thread_id",
              "thread_id_2"
            ],
            "key": "thread_id",
            "used_key_parts": [
              "thread_id"
            ],
            "key_length": "3",
            "ref": [
              "const"
            ],
            "rows_examined_per_scan": 3,
            "rows_produced_per_join": 0,
            "filtered": "10.00",
            "cost_info": {
              "read_cost": "0.75",
              "eval_cost": "0.03",
              "prefix_cost": "1.05",
              "data_read_per_join": "134"
            },
            "used_columns": [
              "post_id",
              "thread_id",
              "name",
              "timestamp",
              "user_id",
              "ip_address",
              "status"
            ],
            "attached_condition": "(`goimagine`.`discussion_posts`.`status` = 'A')"
          }
        },
        {
          "table": {
            "table_name": "discussion_messages",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "post_id"
            ],
            "key_length": "3",
            "ref": [
              "goimagine.discussion_posts.post_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 0,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "0.14",
              "eval_cost": "0.03",
              "prefix_cost": "1.22",
              "data_read_per_join": "7"
            },
            "used_columns": [
              "message",
              "post_id"
            ]
          }
        },
        {
          "table": {
            "table_name": "discussion_rating",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "post_id"
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            "key_length": "3",
            "ref": [
              "goimagine.discussion_posts.post_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 0,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "0.08",
              "eval_cost": "0.03",
              "prefix_cost": "1.32",
              "data_read_per_join": "4"
            },
            "used_columns": [
              "rating_value",
              "post_id"
            ]
          }
        }
      ]
    }
  }
}

Result

post_id thread_id name timestamp user_id ip_address status message rating_value
1257 393 Kimberly Cap/Capable By Design 1647522120 1190 180c3b22 A I have been searching for the perfect coastal themed decor for my office, and I finally found it! I ordered 6 signs, and they are AMAZING!!! They shipped quickly, were packaged very well, and the transaction was easy from start to finish. I even got to watch the process on Instagram. I highly recommend this shop! 5
95 393 Christine Lincoln 1591231200 387 47ae3724 A I had two signs made. At first I just wanted the soak and unwind sign but needed it in different colors to match my bathroom. Terri willingly worked with me to math the colors and change the sign up so it would work for me. She was so kind. I then asked to get the Hope is an anchor sign to work with the other sign. The way I suggested it wouldn't of worked and Terri kindly told me how to better put the signs together. She was wonderful to work with and I LOVE the way the signs came out. She was soooooo wonderful and I am thrilled with how the signs came out. 5
21 393 Karen Eaton 1588788660 280 450f9d52 A I had the Be Still and Know that I am God sign made for my daughter. She LOVED it!! Shipping was fast and sending directly to her was easy with this seller. Highly recommend!! 5