SELECT 
  cscart_companies.company_id, 
  cscart_companies.lang_code, 
  cscart_companies.email, 
  cscart_companies.company, 
  cscart_companies.timestamp, 
  cscart_companies.status, 
  cscart_company_descriptions.company_description, 
  cscart_vendor_plan_descriptions.plan, 
  cscart_seo_names.name as seo_name, 
  cscart_seo_names.path as seo_path, 
  AVG(
    cscart_discussion_rating.rating_value
  ) AS average_rating, 
  CONCAT(
    cscart_companies.company_id, 
    '_', 
    IF (
      cscart_discussion_rating.thread_id, 
      cscart_discussion_rating.thread_id, 
      '0'
    )
  ) AS company_thread_ids 
FROM 
  cscart_companies 
  LEFT JOIN cscart_company_descriptions ON cscart_company_descriptions.company_id = cscart_companies.company_id 
  AND cscart_company_descriptions.lang_code = 'es' 
  LEFT JOIN cscart_vendor_plan_descriptions ON cscart_companies.plan_id = cscart_vendor_plan_descriptions.plan_id 
  AND cscart_vendor_plan_descriptions.lang_code = 'es' 
  LEFT JOIN cscart_seo_names ON cscart_seo_names.object_id = cscart_companies.company_id 
  AND cscart_seo_names.type = 'm' 
  AND cscart_seo_names.dispatch = '' 
  AND cscart_seo_names.lang_code = 'es' 
  LEFT JOIN cscart_discussion ON cscart_discussion.object_id = cscart_companies.company_id 
  AND cscart_discussion.object_type = 'M' 
  LEFT JOIN cscart_discussion_posts ON cscart_discussion_posts.thread_id = cscart_discussion.thread_id 
  AND cscart_discussion_posts.status = 'A' 
  LEFT JOIN cscart_discussion_rating ON cscart_discussion.thread_id = cscart_discussion_rating.thread_id 
  AND cscart_discussion_rating.post_id = cscart_discussion_posts.post_id 
WHERE 
  1 
  AND cscart_companies.status = 'A' 
GROUP BY 
  company_thread_ids 
ORDER BY 
  cscart_companies.company desc 
LIMIT 
  10, 10

Query time 0.00267

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "17.11"
    },
    "ordering_operation": {
      "using_filesort": true,
      "grouping_operation": {
        "using_temporary_table": true,
        "using_filesort": false,
        "nested_loop": [
          {
            "table": {
              "table_name": "cscart_companies",
              "access_type": "ALL",
              "rows_examined_per_scan": 13,
              "rows_produced_per_join": 1,
              "filtered": "10.00",
              "cost_info": {
                "read_cost": "5.55",
                "eval_cost": "0.26",
                "prefix_cost": "5.81",
                "data_read_per_join": "20K"
              },
              "used_columns": [
                "company_id",
                "status",
                "company",
                "lang_code",
                "email",
                "timestamp",
                "plan_id"
              ],
              "attached_condition": "(`marketpl_db`.`cscart_companies`.`status` = 'A')"
            }
          },
          {
            "table": {
              "table_name": "cscart_company_descriptions",
              "access_type": "eq_ref",
              "possible_keys": [
                "PRIMARY"
              ],
              "key": "PRIMARY",
              "used_key_parts": [
                "company_id",
                "lang_code"
              ],
              "key_length": "10",
              "ref": [
                "marketpl_db.cscart_companies.company_id",
                "const"
              ],
              "rows_examined_per_scan": 1,
              "rows_produced_per_join": 1,
              "filtered": "100.00",
              "cost_info": {
                "read_cost": "1.30",
                "eval_cost": "0.26",
                "prefix_cost": "7.37",
                "data_read_per_join": "52"
              },
              "used_columns": [
                "company_id",
                "lang_code",
                "company_description"
              ]
            }
          },
          {
            "table": {
              "table_name": "cscart_vendor_plan_descriptions",
              "access_type": "eq_ref",
              "possible_keys": [
                "PRIMARY"
              ],
              "key": "PRIMARY",
              "used_key_parts": [
                "plan_id",
                "lang_code"
              ],
              "key_length": "10",
              "ref": [
                "marketpl_db.cscart_companies.plan_id",
                "const"
              ],
              "rows_examined_per_scan": 1,
              "rows_produced_per_join": 1,
              "filtered": "100.00",
              "cost_info": {
                "read_cost": "1.30",
                "eval_cost": "0.26",
                "prefix_cost": "8.93",
                "data_read_per_join": "1K"
              },
              "used_columns": [
                "plan_id",
                "lang_code",
                "plan"
              ]
            }
          },
          {
            "table": {
              "table_name": "cscart_seo_names",
              "access_type": "ref",
              "possible_keys": [
                "PRIMARY",
                "dispatch"
              ],
              "key": "PRIMARY",
              "used_key_parts": [
                "object_id",
                "type",
                "dispatch",
                "lang_code"
              ],
              "key_length": "206",
              "ref": [
                "marketpl_db.cscart_companies.company_id",
                "const",
                "const",
                "const"
              ],
              "rows_examined_per_scan": 1,
              "rows_produced_per_join": 1,
              "filtered": "100.00",
              "cost_info": {
                "read_cost": "1.30",
                "eval_cost": "0.26",
                "prefix_cost": "10.49",
                "data_read_per_join": "2K"
              },
              "used_columns": [
                "name",
                "object_id",
                "type",
                "dispatch",
                "path",
                "lang_code"
              ],
              "attached_condition": "<if>(is_not_null_compl(cscart_seo_names), (`marketpl_db`.`cscart_seo_names`.`object_id` = `marketpl_db`.`cscart_companies`.`company_id`), true)"
            }
          },
          {
            "table": {
              "table_name": "cscart_discussion",
              "access_type": "eq_ref",
              "possible_keys": [
                "object_id"
              ],
              "key": "object_id",
              "used_key_parts": [
                "object_id",
                "object_type"
              ],
              "key_length": "6",
              "ref": [
                "marketpl_db.cscart_companies.company_id",
                "const"
              ],
              "rows_examined_per_scan": 1,
              "rows_produced_per_join": 1,
              "filtered": "100.00",
              "cost_info": {
                "read_cost": "1.30",
                "eval_cost": "0.26",
                "prefix_cost": "12.05",
                "data_read_per_join": "20"
              },
              "used_columns": [
                "thread_id",
                "object_id",
                "object_type"
              ],
              "attached_condition": "<if>(is_not_null_compl(cscart_discussion), (`marketpl_db`.`cscart_discussion`.`object_id` = `marketpl_db`.`cscart_companies`.`company_id`), true)"
            }
          },
          {
            "table": {
              "table_name": "cscart_discussion_posts",
              "access_type": "ALL",
              "possible_keys": [
                "thread_id",
                "thread_id_2"
              ],
              "rows_examined_per_scan": 2,
              "rows_produced_per_join": 2,
              "filtered": "100.00",
              "using_join_buffer": "Block Nested Loop",
              "cost_info": {
                "read_cost": "2.02",
                "eval_cost": "0.52",
                "prefix_cost": "14.59",
                "data_read_per_join": "1K"
              },
              "used_columns": [
                "post_id",
                "thread_id",
                "status"
              ],
              "attached_condition": "<if>(is_not_null_compl(cscart_discussion_posts), ((`marketpl_db`.`cscart_discussion_posts`.`thread_id` = `marketpl_db`.`cscart_discussion`.`thread_id`) and (`marketpl_db`.`cscart_discussion_posts`.`status` = 'A')), true)"
            }
          },
          {
            "table": {
              "table_name": "cscart_discussion_rating",
              "access_type": "eq_ref",
              "possible_keys": [
                "PRIMARY",
                "thread_id"
              ],
              "key": "PRIMARY",
              "used_key_parts": [
                "post_id"
              ],
              "key_length": "3",
              "ref": [
                "marketpl_db.cscart_discussion_posts.post_id"
              ],
              "rows_examined_per_scan": 1,
              "rows_produced_per_join": 2,
              "filtered": "100.00",
              "cost_info": {
                "read_cost": "2.00",
                "eval_cost": "0.52",
                "prefix_cost": "17.11",
                "data_read_per_join": "41"
              },
              "used_columns": [
                "rating_value",
                "post_id",
                "thread_id"
              ],
              "attached_condition": "<if>(is_not_null_compl(cscart_discussion_rating), (`marketpl_db`.`cscart_discussion_rating`.`thread_id` = `marketpl_db`.`cscart_discussion`.`thread_id`), true)"
            }
          }
        ]
      }
    }
  }
}