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 (
    51497, 51498, 51496, 105, 126, 115, 11, 
    81, 56, 135, 82, 116, 117, 106, 17, 57, 
    122, 58, 5, 22, 18, 27, 121, 119, 141, 
    23, 4, 142, 120, 62, 108, 107, 10, 16, 
    114, 118, 13, 61, 15, 9, 59, 123, 60, 113, 
    6, 14, 63
  ) 
  AND pfv.lang_code = 'ru'

Query time 0.00256

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "56.88"
    },
    "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": 97,
          "rows_produced_per_join": 97,
          "filtered": "100.00",
          "using_index": true,
          "cost_info": {
            "read_cost": "10.92",
            "eval_cost": "9.70",
            "prefix_cost": "20.62",
            "data_read_per_join": "75K"
          },
          "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 (51497,51498,51496,105,126,115,11,81,56,135,82,116,117,106,17,57,122,58,5,22,18,27,121,119,141,23,4,142,120,62,108,107,10,16,114,118,13,61,15,9,59,123,60,113,6,14,63)) 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": 6,
          "filtered": "6.81",
          "cost_info": {
            "read_cost": "24.25",
            "eval_cost": "0.66",
            "prefix_cost": "54.57",
            "data_read_per_join": "10K"
          },
          "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": 6,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "1.65",
            "eval_cost": "0.66",
            "prefix_cost": "56.88",
            "data_read_per_join": "20K"
          },
          "used_columns": [
            "variant_id",
            "variant",
            "lang_code"
          ]
        }
      }
    ]
  }
}