SELECT 
  SQL_CALC_FOUND_ROWS products.product_id, 
  IF(
    shared_descr.product_id IS NOT NULL, 
    shared_descr.product, descr1.product
  ) as product, 
  stoc_intern, 
  pret_achizitie, 
  pret_revanzator, 
  gestiune 
FROM 
  cscart_products as products 
  LEFT JOIN cscart_product_options_inventory as inventory ON inventory.product_id = products.product_id 
  LEFT JOIN cscart_product_descriptions as descr1 ON descr1.product_id = products.product_id 
  AND descr1.lang_code = 'ro' 
  LEFT JOIN cscart_product_prices as prices ON prices.product_id = products.product_id 
  AND prices.lower_limit = 1 
  INNER JOIN cscart_products_categories as products_categories ON products_categories.product_id = products.product_id 
  INNER JOIN cscart_categories ON cscart_categories.category_id = products_categories.category_id 
  AND (
    cscart_categories.usergroup_ids = '' 
    OR FIND_IN_SET(
      0, cscart_categories.usergroup_ids
    ) 
    OR FIND_IN_SET(
      1, cscart_categories.usergroup_ids
    )
  ) 
  AND cscart_categories.status IN ('A', 'H') 
  LEFT JOIN cscart_ult_product_descriptions shared_descr ON shared_descr.product_id = products.product_id 
  AND shared_descr.company_id = 1 
  AND shared_descr.lang_code = 'ro' 
  LEFT JOIN cscart_product_popularity as popularity ON popularity.product_id = products.product_id 
WHERE 
  1 
  AND cscart_categories.category_id IN (
    8180, 21142, 21158, 8181, 8200, 8215, 
    8248, 8278, 8312, 8318, 8320, 8330, 
    8349, 8360, 8381, 8387, 8392, 8398, 
    8406, 8420, 8457, 8465, 8472, 8479, 
    8481, 8484, 8485, 8513, 8552, 8585, 
    8619
  ) 
  AND cscart_categories.company_id = 1 
  AND (
    CASE products.tracking WHEN 'O' THEN inventory.amount > 0 WHEN 'B' THEN products.amount > 0 ELSE 1 END
  ) 
  AND (
    products.usergroup_ids = '' 
    OR FIND_IN_SET(0, products.usergroup_ids) 
    OR FIND_IN_SET(1, products.usergroup_ids)
  ) 
  AND products.status IN ('A') 
  AND prices.usergroup_id IN (0, 0, 1) 
GROUP BY 
  products.product_id 
ORDER BY 
  popularity.total desc, 
  product_id ASC 
LIMIT 
  0, 36

Query time 0.01452

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "36.43"
    },
    "ordering_operation": {
      "using_filesort": true,
      "grouping_operation": {
        "using_temporary_table": true,
        "using_filesort": false,
        "nested_loop": [
          {
            "table": {
              "table_name": "inventory",
              "access_type": "system",
              "possible_keys": [
                "pc"
              ],
              "rows_examined_per_scan": 0,
              "rows_produced_per_join": 1,
              "filtered": "0.00",
              "const_row_not_found": true,
              "cost_info": {
                "read_cost": "0.00",
                "eval_cost": "0.10",
                "prefix_cost": "0.00",
                "data_read_per_join": "880"
              },
              "used_columns": [
                "product_id",
                "amount"
              ]
            }
          },
          {
            "table": {
              "table_name": "cscart_categories",
              "access_type": "range",
              "possible_keys": [
                "PRIMARY",
                "c_status",
                "p_category_id"
              ],
              "key": "PRIMARY",
              "used_key_parts": [
                "category_id"
              ],
              "key_length": "3",
              "rows_examined_per_scan": 31,
              "rows_produced_per_join": 0,
              "filtered": "2.00",
              "cost_info": {
                "read_cost": "32.60",
                "eval_cost": "0.06",
                "prefix_cost": "32.67",
                "data_read_per_join": "1K"
              },
              "used_columns": [
                "category_id",
                "company_id",
                "usergroup_ids",
                "status"
              ],
              "attached_condition": "((`maniamall_cscart`.`cscart_categories`.`company_id` = 1) and (`maniamall_cscart`.`cscart_categories`.`category_id` in (8180,21142,21158,8181,8200,8215,8248,8278,8312,8318,8320,8330,8349,8360,8381,8387,8392,8398,8406,8420,8457,8465,8472,8479,8481,8484,8485,8513,8552,8585,8619)) and ((`maniamall_cscart`.`cscart_categories`.`usergroup_ids` = '') or (0 <> find_in_set(0,`maniamall_cscart`.`cscart_categories`.`usergroup_ids`)) or (0 <> find_in_set(1,`maniamall_cscart`.`cscart_categories`.`usergroup_ids`))) and (`maniamall_cscart`.`cscart_categories`.`status` in ('A','H')))"
            }
          },
          {
            "table": {
              "table_name": "products_categories",
              "access_type": "ref",
              "possible_keys": [
                "PRIMARY",
                "pt"
              ],
              "key": "PRIMARY",
              "used_key_parts": [
                "category_id"
              ],
              "key_length": "3",
              "ref": [
                "maniamall_cscart.cscart_categories.category_id"
              ],
              "rows_examined_per_scan": 19,
              "rows_produced_per_join": 12,
              "filtered": "100.00",
              "using_index": true,
              "cost_info": {
                "read_cost": "0.60",
                "eval_cost": "1.21",
                "prefix_cost": "34.47",
                "data_read_per_join": "193"
              },
              "used_columns": [
                "product_id",
                "category_id"
              ]
            }
          },
          {
            "table": {
              "table_name": "products",
              "access_type": "eq_ref",
              "possible_keys": [
                "PRIMARY",
                "status"
              ],
              "key": "PRIMARY",
              "used_key_parts": [
                "product_id"
              ],
              "key_length": "3",
              "ref": [
                "maniamall_cscart.products_categories.product_id"
              ],
              "rows_examined_per_scan": 1,
              "rows_produced_per_join": 0,
              "filtered": "5.00",
              "cost_info": {
                "read_cost": "0.00",
                "eval_cost": "0.06",
                "prefix_cost": "35.68",
                "data_read_per_join": "2K"
              },
              "used_columns": [
                "product_id",
                "status",
                "amount",
                "usergroup_ids",
                "tracking",
                "stoc_intern",
                "pret_achizitie",
                "pret_revanzator",
                "gestiune"
              ],
              "attached_condition": "((0 <> (case `maniamall_cscart`.`products`.`tracking` when 'O' then <cache>((NULL > 0)) when 'B' then (`maniamall_cscart`.`products`.`amount` > 0) else 1 end)) and ((`maniamall_cscart`.`products`.`usergroup_ids` = '') or (0 <> find_in_set(0,`maniamall_cscart`.`products`.`usergroup_ids`)) or (0 <> find_in_set(1,`maniamall_cscart`.`products`.`usergroup_ids`))) and (`maniamall_cscart`.`products`.`status` = 'A'))"
            }
          },
          {
            "table": {
              "table_name": "shared_descr",
              "access_type": "eq_ref",
              "possible_keys": [
                "PRIMARY",
                "product_id",
                "company_id"
              ],
              "key": "PRIMARY",
              "used_key_parts": [
                "product_id",
                "lang_code",
                "company_id"
              ],
              "key_length": "13",
              "ref": [
                "maniamall_cscart.products_categories.product_id",
                "const",
                "const"
              ],
              "rows_examined_per_scan": 1,
              "rows_produced_per_join": 0,
              "filtered": "100.00",
              "cost_info": {
                "read_cost": "0.00",
                "eval_cost": "0.06",
                "prefix_cost": "35.74",
                "data_read_per_join": "2K"
              },
              "used_columns": [
                "product_id",
                "lang_code",
                "company_id",
                "product"
              ]
            }
          },
          {
            "table": {
              "table_name": "descr1",
              "access_type": "eq_ref",
              "possible_keys": [
                "PRIMARY",
                "product_id"
              ],
              "key": "PRIMARY",
              "used_key_parts": [
                "product_id",
                "lang_code"
              ],
              "key_length": "9",
              "ref": [
                "maniamall_cscart.products_categories.product_id",
                "const"
              ],
              "rows_examined_per_scan": 1,
              "rows_produced_per_join": 0,
              "filtered": "100.00",
              "cost_info": {
                "read_cost": "0.00",
                "eval_cost": "0.06",
                "prefix_cost": "35.80",
                "data_read_per_join": "2K"
              },
              "used_columns": [
                "product_id",
                "lang_code",
                "product"
              ]
            }
          },
          {
            "table": {
              "table_name": "popularity",
              "access_type": "eq_ref",
              "possible_keys": [
                "PRIMARY",
                "total"
              ],
              "key": "PRIMARY",
              "used_key_parts": [
                "product_id"
              ],
              "key_length": "3",
              "ref": [
                "maniamall_cscart.products_categories.product_id"
              ],
              "rows_examined_per_scan": 1,
              "rows_produced_per_join": 0,
              "filtered": "100.00",
              "cost_info": {
                "read_cost": "0.00",
                "eval_cost": "0.06",
                "prefix_cost": "35.86",
                "data_read_per_join": "19"
              },
              "used_columns": [
                "product_id",
                "total"
              ]
            }
          },
          {
            "table": {
              "table_name": "prices",
              "access_type": "ref",
              "possible_keys": [
                "usergroup",
                "product_id",
                "lower_limit",
                "usergroup_id"
              ],
              "key": "lower_limit",
              "used_key_parts": [
                "lower_limit",
                "product_id"
              ],
              "key_length": "6",
              "ref": [
                "const",
                "maniamall_cscart.products_categories.product_id"
              ],
              "rows_examined_per_scan": 1,
              "rows_produced_per_join": 0,
              "filtered": "50.00",
              "using_index": true,
              "cost_info": {
                "read_cost": "0.51",
                "eval_cost": "0.03",
                "prefix_cost": "36.43",
                "data_read_per_join": "7"
              },
              "used_columns": [
                "product_id",
                "lower_limit",
                "usergroup_id"
              ],
              "attached_condition": "(`maniamall_cscart`.`prices`.`usergroup_id` in (0,0,1))"
            }
          }
        ]
      }
    }
  }
}

Result

product_id product stoc_intern pret_achizitie pret_revanzator gestiune
596382 Suport numar inmatriculare auto carbon Kft Auto -99 0.00 0.00 N
590365 Cupla aer M6XM8XM6 , mufa rapida teu , reductie plastic Kft Auto -99 0.00 0.00 N
590359 Cupla aer M4 la M6, mufa rapida dreapta , reductie plastic Kft Auto -99 0.00 0.00 N
590343 Cupla aer M12 , mufa rapida dreapta, plastic Kft Auto -99 0.00 0.00 N
590337 Cupla aer M10 , mufa rapida teu , plastic Kft Auto -99 0.00 0.00 N
590566 Fierbator apa electric pentru masina , 12V, 150W, Carpoint Kft Auto -99 0.00 0.00 Y
590341 Cupla aer M12 , mufa rapida cot 90 grade, plastic Kft Auto -99 0.00 0.00 Y
590335 Cupla aer M10 , mufa rapida cot 90 grade, plastic Kft Auto -99 0.00 0.00 N
590366 Cupla aer M8 , mufa rapida cot 90 grade, plastic Kft Auto -99 0.00 0.00 N
590358 Cupla aer M4 , mufa rapida teu , plastic Kft Auto -99 0.00 0.00 N
589041 Cabluri transfer curent baterii Carpoint , lungime 2.5m, grosime cablu 25mm2 Kft Auto -99 0.00 0.00 N
590364 Cupla aer M6XM4XM6 , mufa rapida teu , reductie plastic Kft Auto -99 0.00 0.00 N
590369 Cupla aer M8 , mufa rapida teu , plastic Kft Auto -99 0.00 0.00 N
590368 Cupla aer M8 , mufa rapida dreapta , plastic Kft Auto -99 0.00 0.00 N
589374 Catadioptru reflectorizant rotund Portocaliu universal BestAutoVest, fixare cu surub, 50 mm , 1 buc. Kft Auto -99 0.00 0.00 N
590348 Cupla aer M14 , mufa rapida cot 90 grade, plastic Kft Auto -99 0.00 0.00 N
1070392 Cupla aer M6 , mufa rapida teu , plastic Kft Auto -99 0.00 0.00 N
590356 Cupla aer M16 , mufa rapida teu , plastic Kft Auto -99 0.00 0.00 N
590351 Cupla aer M14 , mufa rapida teu , plastic Kft Auto -99 0.00 0.00 N
590350 Cupla aer M14 , mufa rapida dreapta , plastic Kft Auto -99 0.00 0.00 N
589033 Cabluri transfer curent baterii Automax , lungime 4.5m, 600A Kft Auto -99 0.00 0.00 N
590755 Furtun umflat roti camioane 12 Metri culoare albastru Kft Auto -99 0.00 0.00 N
1070391 Cupla aer M4 , mufa rapida cot 90 grade, plastic Kft Auto -99 0.00 0.00 N
590355 Cupla aer M16 , mufa rapida dreapta , plastic Kft Auto -99 0.00 0.00 N
588389 Bec auto Automax cu alarma mers inapoi 24V BAY15S , 1 buc. Kft Auto -99 0.00 0.00 N