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 (28759) 
  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 0.00627

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "83.01"
    },
    "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": "const",
              "possible_keys": [
                "PRIMARY",
                "c_status",
                "p_category_id"
              ],
              "key": "PRIMARY",
              "used_key_parts": [
                "category_id"
              ],
              "key_length": "3",
              "ref": [
                "const"
              ],
              "rows_examined_per_scan": 1,
              "rows_produced_per_join": 1,
              "filtered": "100.00",
              "cost_info": {
                "read_cost": "0.00",
                "eval_cost": "0.10",
                "prefix_cost": "0.00",
                "data_read_per_join": "2K"
              },
              "used_columns": [
                "category_id",
                "company_id",
                "usergroup_ids",
                "status"
              ]
            }
          },
          {
            "table": {
              "table_name": "products_categories",
              "access_type": "ref",
              "possible_keys": [
                "PRIMARY",
                "pt"
              ],
              "key": "PRIMARY",
              "used_key_parts": [
                "category_id"
              ],
              "key_length": "3",
              "ref": [
                "const"
              ],
              "rows_examined_per_scan": 312,
              "rows_produced_per_join": 312,
              "filtered": "100.00",
              "using_index": true,
              "cost_info": {
                "read_cost": "1.43",
                "eval_cost": "31.20",
                "prefix_cost": "32.63",
                "data_read_per_join": "4K"
              },
              "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": 15,
              "filtered": "5.00",
              "cost_info": {
                "read_cost": "0.00",
                "eval_cost": "1.56",
                "prefix_cost": "63.83",
                "data_read_per_join": "68K"
              },
              "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": 15,
              "filtered": "100.00",
              "cost_info": {
                "read_cost": "0.00",
                "eval_cost": "1.56",
                "prefix_cost": "65.39",
                "data_read_per_join": "59K"
              },
              "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": 15,
              "filtered": "100.00",
              "cost_info": {
                "read_cost": "0.00",
                "eval_cost": "1.56",
                "prefix_cost": "66.95",
                "data_read_per_join": "59K"
              },
              "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": 15,
              "filtered": "100.00",
              "cost_info": {
                "read_cost": "0.00",
                "eval_cost": "1.56",
                "prefix_cost": "68.51",
                "data_read_per_join": "499"
              },
              "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": 7,
              "filtered": "50.00",
              "using_index": true,
              "cost_info": {
                "read_cost": "12.94",
                "eval_cost": "0.78",
                "prefix_cost": "83.01",
                "data_read_per_join": "187"
              },
              "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
1128285 Set perne decorative pentru mobilier paleti, perna sezut 120x70 cm + perna spate 120x40 cm, culoare gri 0 0.00 19.00 Y
1128289 Set perne decorative pentru mobilier paleti,perna sezut 120x70 cm + perna spate 120x40 cm, culoare bej 0 0.00 19.00 Y
1129605 Set perne decorative pentru mobilier paleti, perna sezut 120x70 cm + perna spate 120x40 cm culoare galben 0 0.00 19.00 Y
1129852 Set perne decorative pentru Balansoar, leagan sau bancuta, perna sezut 180x55 + perna spate 180x55, culoare galben -99 0.00 215.00 Y
1128299 Set perne decorative pentru mobilier paleti, perna sezut 120x70 cm + perna spate 120x40 cm, culoare mov 0 0.00 19.00 Y
1346803 Perna decorativa pentru scaun de bucatarie cu spatar, dimensiune sezut 42x40 cm, spatar 42x50 cm, culoare gri -99 0.00 52.00 Y
1128294 Set perne decorative pentru mobilier paleti, perna sezut 120x70 cm + perna spate 120x40 cm, culoare albastru 0 0.00 19.00 Y
1129606 Set perne decorative pentru mobilier paleti, perna sezut 120x70 cm + perna spate 120x40 cm, culoare alb 0 0.00 19.00 Y
1128290 Set perne decorative pentru mobilier paleti, perna sezut 120x70 cm + perna spate 120x40 cm, culoare negru 0 0.00 19.00 Y
1129597 Perna decorativa rotunda, pentru scaun de bucatarie sau terasa, diametrul 35cm, culoare galben -99 0.00 19.00 Y
1128097 Perna decorativa rotunda, pentru scaun de bucatarie sau terasa, diametrul 35cm, culoare gri inchis -99 0.00 19.00 Y
1128078 Perna decorativa pentru scaun de bucatarie sau terasa, dimensiuni 40x40cm, culoare Gri -99 0.00 19.00 Y
1193387 Perna decorativa patrata, 40x40 cm, pentru canapele, plina cu Puf Mania Relax, culoare albastru -99 0.00 23.00 Y
1198929 Perna decorativa dreptunghiulara, 50x30 cm, plina cu Puf Mania Relax, culoare galben -99 0.00 23.00 Y
1198866 Perna decorativa dreptunghiulara Mania Relax, din bumbac, 50x70 cm, culoare verde -99 0.00 42.00 Y
1198921 Perna decorativa dreptunghiulara, 50x30 cm, plina cu Puf Mania Relax, culoare maro -99 0.00 23.00 Y
1346809 Perna decorativa pentru scaun de bucatarie cu spatar, dimensiune sezut 42x40 cm, spatar 42x50 cm, culoare mov -99 0.00 52.00 Y
1346810 Perna decorativa pentru scaun de bucatarie cu spatar, dimensiune sezut 42x40 cm, spatar 42x50 cm, culoare verde -99 0.00 52.00 Y
2538988 Perna de gradina matlasata cu umplutura moale pentru leagan sau banca, perna sezut 140x60 cm + perna spate 140x50 cm, culoare gri -99 85.83 145.00 Y