SELECT 
  product_id, 
  feature_id, 
  variant_id 
FROM 
  cscart_product_features_values 
WHERE 
  product_id IN (
    13267, 13268, 13269, 13270, 13271, 13272, 
    13273
  ) 
  AND feature_id IN (
    595, 628, 627, 624, 625, 553, 626, 622, 
    623, 646, 647, 636, 637
  ) 
  AND lang_code = 'en'

Query time 0.00540

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "7.02"
    },
    "table": {
      "table_name": "cscart_product_features_values",
      "access_type": "range",
      "possible_keys": [
        "PRIMARY",
        "fl",
        "lang_code",
        "product_id",
        "fpl",
        "idx_product_feature_variant_id"
      ],
      "key": "PRIMARY",
      "used_key_parts": [
        "feature_id",
        "product_id",
        "variant_id",
        "lang_code"
      ],
      "key_length": "15",
      "rows_examined_per_scan": 17,
      "rows_produced_per_join": 17,
      "filtered": "100.00",
      "using_index_for_skip_scan": true,
      "cost_info": {
        "read_cost": "5.32",
        "eval_cost": "1.70",
        "prefix_cost": "7.02",
        "data_read_per_join": "13K"
      },
      "used_columns": [
        "feature_id",
        "product_id",
        "variant_id",
        "lang_code"
      ],
      "attached_condition": "((`test2_gaseus`.`cscart_product_features_values`.`product_id` in (13267,13268,13269,13270,13271,13272,13273)) and (`test2_gaseus`.`cscart_product_features_values`.`feature_id` in (595,628,627,624,625,553,626,622,623,646,647,636,637)) and (`test2_gaseus`.`cscart_product_features_values`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id feature_id variant_id
13267 553 1912
13268 553 1912
13269 553 1912
13270 553 1912
13271 553 1912
13272 553 1912
13273 553 1912
13267 595 1904
13268 595 1905
13269 595 1789
13270 595 2499
13271 595 1787
13272 595 1900
13273 595 1899
13267 622 2497
13268 622 2497
13269 622 2497
13270 622 2497
13271 622 2497
13272 622 2497
13273 622 2497
13267 623 2524
13268 623 2524
13269 623 2524
13270 623 2524
13271 623 2524
13272 623 2524
13273 623 2524
13267 624 1803
13268 624 1803
13269 624 1803
13270 624 1803
13271 624 1803
13272 624 1803
13273 624 1803
13267 625 2122
13268 625 2122
13269 625 2122
13270 625 2122
13271 625 2122
13272 625 2122
13273 625 2122
13267 626 2043
13268 626 2043
13269 626 2043
13270 626 2043
13271 626 2043
13272 626 2043
13273 626 2043
13267 627 2378
13268 627 2378
13269 627 2378
13270 627 2378
13271 627 2378
13272 627 2378
13273 627 2378
13267 628 1660
13268 628 1660
13269 628 1660
13270 628 1660
13271 628 1660
13272 628 1660
13273 628 1660
13267 636 2348
13268 636 2348
13269 636 2348
13270 636 2348
13271 636 2348
13272 636 2348
13273 636 2348
13267 637 2345
13268 637 2345
13269 637 2345
13270 637 2345
13271 637 2345
13272 637 2345
13273 637 2345
13267 646 2370
13268 646 2370
13269 646 2370
13270 646 2370
13271 646 2370
13272 646 2370
13273 646 2370
13267 647 2374
13268 647 2374
13269 647 2374
13270 647 2374
13271 647 2374
13272 647 2374
13273 647 2374