SELECT 
  pfv.feature_id, 
  pfv.product_id, 
  pfv.variant_id, 
  fv.position, 
  fvd.variant 
FROM 
  cscart_product_features_values AS pfv 
  INNER JOIN cscart_product_feature_variants AS fv ON pfv.feature_id = fv.feature_id 
  AND pfv.variant_id = fv.variant_id 
  INNER JOIN cscart_product_feature_variant_descriptions AS fvd ON pfv.variant_id = fvd.variant_id 
  AND fvd.lang_code = 'ru' 
WHERE 
  pfv.feature_id IN (193, 3) 
  AND pfv.product_id IN (
    51567, 51565, 51564, 139, 129, 51566, 
    51301, 51, 50, 51497, 51498, 53, 22713, 
    21, 22714, 22712, 46, 22715, 22716, 
    51496, 21567, 91, 50989, 105, 48, 49, 
    92, 137, 88, 126, 31, 51358, 115, 80, 
    37, 11, 140, 41, 30, 90, 38, 124, 81, 56, 
    82, 116, 117, 125, 106, 39, 40, 22710, 
    22711, 17, 57, 122, 58, 5
  ) 
  AND pfv.lang_code = 'ru'

Query time 0.00324

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "72.06"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "pfv",
          "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",
          "used_key_parts": [
            "product_id",
            "feature_id",
            "lang_code"
          ],
          "key_length": "12",
          "rows_examined_per_scan": 123,
          "rows_produced_per_join": 123,
          "filtered": "100.00",
          "using_index": true,
          "cost_info": {
            "read_cost": "13.78",
            "eval_cost": "12.30",
            "prefix_cost": "26.08",
            "data_read_per_join": "95K"
          },
          "used_columns": [
            "feature_id",
            "product_id",
            "variant_id",
            "lang_code"
          ],
          "attached_condition": "((`test_uchur_k`.`pfv`.`feature_id` in (193,3)) and (`test_uchur_k`.`pfv`.`product_id` in (51567,51565,51564,139,129,51566,51301,51,50,51497,51498,53,22713,21,22714,22712,46,22715,22716,51496,21567,91,50989,105,48,49,92,137,88,126,31,51358,115,80,37,11,140,41,30,90,38,124,81,56,82,116,117,125,106,39,40,22710,22711,17,57,122,58,5)) and (`test_uchur_k`.`pfv`.`lang_code` = 'ru'))"
        }
      },
      {
        "table": {
          "table_name": "fv",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY",
            "feature_id"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "variant_id"
          ],
          "key_length": "3",
          "ref": [
            "test_uchur_k.pfv.variant_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 8,
          "filtered": "6.81",
          "cost_info": {
            "read_cost": "30.75",
            "eval_cost": "0.84",
            "prefix_cost": "69.13",
            "data_read_per_join": "12K"
          },
          "used_columns": [
            "variant_id",
            "feature_id",
            "position"
          ],
          "attached_condition": "(`test_uchur_k`.`fv`.`feature_id` = `test_uchur_k`.`pfv`.`feature_id`)"
        }
      },
      {
        "table": {
          "table_name": "fvd",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "variant_id",
            "lang_code"
          ],
          "key_length": "9",
          "ref": [
            "test_uchur_k.pfv.variant_id",
            "const"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 8,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "2.09",
            "eval_cost": "0.84",
            "prefix_cost": "72.06",
            "data_read_per_join": "26K"
          },
          "used_columns": [
            "variant_id",
            "variant",
            "lang_code"
          ]
        }
      }
    ]
  }
}