SELECT 
  v.product_id, 
  v.feature_id, 
  v.value, 
  v.value_int, 
  v.variant_id, 
  f.feature_type, 
  fd.description, 
  fd.prefix, 
  fd.suffix, 
  vd.variant, 
  f.parent_id, 
  f.position, 
  gf.position as gposition 
FROM 
  cscart_product_features as f 
  LEFT JOIN cscart_product_features_values as v ON v.feature_id = f.feature_id 
  LEFT JOIN cscart_product_features_descriptions as fd ON fd.feature_id = v.feature_id 
  AND fd.lang_code = 'ru' 
  LEFT JOIN cscart_product_feature_variants fv ON fv.variant_id = v.variant_id 
  LEFT JOIN cscart_product_feature_variant_descriptions as vd ON vd.variant_id = fv.variant_id 
  AND vd.lang_code = 'ru' 
  LEFT JOIN cscart_product_features as gf ON gf.feature_id = f.parent_id 
  AND gf.feature_type = 'G' 
WHERE 
  f.status IN ('A') 
  AND v.product_id in (
    5094, 5075, 5074, 5068, 5350, 5082, 4708, 
    4707, 4706, 4652, 4627, 4628, 4651, 
    4677, 4679, 4678, 5070, 4344, 5071, 
    19544, 5347, 4637, 4671, 4638
  ) 
  AND f.display_on_catalog = 'Y' 
  AND (
    f.categories_path = '' 
    OR FIND_IN_SET(303, f.categories_path) 
    OR FIND_IN_SET(304, f.categories_path) 
    OR FIND_IN_SET(315, f.categories_path)
  ) 
  AND IF(
    f.parent_id, 
    (
      SELECT 
        status 
      FROM 
        cscart_product_features as df 
      WHERE 
        df.feature_id = f.parent_id
    ), 
    'A'
  ) IN ('A') 
  AND (
    v.variant_id != 0 
    OR (
      f.feature_type != 'C' 
      AND v.value != ''
    ) 
    OR (f.feature_type = 'C') 
    OR v.value_int != ''
  ) 
  AND v.lang_code = 'ru' 
ORDER BY 
  fd.description, 
  fv.position

Query time 0.01082

JSON explain

{
  "query_block": {
    "select_id": 1,
    "filesort": {
      "sort_key": "fd.description, fv.position",
      "temporary_table": {
        "table": {
          "table_name": "v",
          "access_type": "range",
          "possible_keys": [
            "PRIMARY",
            "fl",
            "variant_id",
            "lang_code",
            "product_id",
            "fpl",
            "idx_product_feature_variant_id"
          ],
          "key": "idx_product_feature_variant_id",
          "key_length": "3",
          "used_key_parts": ["product_id"],
          "rows": 126,
          "filtered": 75.397,
          "index_condition": "v.product_id in (5094,5075,5074,5068,5350,5082,4708,4707,4706,4652,4627,4628,4651,4677,4679,4678,5070,4344,5071,19544,5347,4637,4671,4638) and v.lang_code = 'ru'"
        },
        "table": {
          "table_name": "f",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY", "status"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["feature_id"],
          "ref": ["admin_test.v.feature_id"],
          "rows": 1,
          "filtered": 100,
          "attached_condition": "f.`status` = 'A' and f.display_on_catalog = 'Y' and (f.categories_path = '' or find_in_set(303,f.categories_path) or find_in_set(304,f.categories_path) or find_in_set(315,f.categories_path)) and if(f.parent_id,(subquery#2),'A') = 'A' and (v.variant_id <> 0 or f.feature_type <> 'C' and v.`value` <> '' or f.feature_type = 'C' or v.value_int <> '')"
        },
        "table": {
          "table_name": "fd",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "9",
          "used_key_parts": ["feature_id", "lang_code"],
          "ref": ["admin_test.v.feature_id", "const"],
          "rows": 1,
          "filtered": 100,
          "attached_condition": "trigcond(fd.lang_code = 'ru')"
        },
        "table": {
          "table_name": "fv",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["variant_id"],
          "ref": ["admin_test.v.variant_id"],
          "rows": 1,
          "filtered": 100
        },
        "table": {
          "table_name": "vd",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "9",
          "used_key_parts": ["variant_id", "lang_code"],
          "ref": ["admin_test.fv.variant_id", "const"],
          "rows": 1,
          "filtered": 100,
          "attached_condition": "trigcond(vd.lang_code = 'ru' and trigcond(fv.variant_id is not null))"
        },
        "table": {
          "table_name": "gf",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["feature_id"],
          "ref": ["admin_test.f.parent_id"],
          "rows": 1,
          "filtered": 100,
          "attached_condition": "trigcond(gf.feature_type = 'G')"
        },
        "subqueries": [
          {
            "expression_cache": {
              "state": "uninitialized",
              "query_block": {
                "select_id": 2,
                "table": {
                  "table_name": "df",
                  "access_type": "eq_ref",
                  "possible_keys": ["PRIMARY"],
                  "key": "PRIMARY",
                  "key_length": "3",
                  "used_key_parts": ["feature_id"],
                  "ref": ["admin_test.f.parent_id"],
                  "rows": 1,
                  "filtered": 100
                }
              }
            }
          }
        ]
      }
    }
  }
}