SELECT 
  product_id, 
  feature_id, 
  variant_id 
FROM 
  cscart_product_features_values 
WHERE 
  product_id IN (
    13014, 13015, 13016, 13017, 13018, 13019, 
    13020, 13021, 13022, 13023, 13024, 
    13025, 13026, 13027
  ) 
  AND feature_id IN (
    646, 647, 595, 628, 627, 624, 625, 553, 
    626, 622, 623, 636, 637
  ) 
  AND lang_code = 'en'

Query time 0.00960

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "11.09"
    },
    "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": 32,
      "rows_produced_per_join": 32,
      "filtered": "100.00",
      "using_index_for_skip_scan": true,
      "cost_info": {
        "read_cost": "7.89",
        "eval_cost": "3.20",
        "prefix_cost": "11.09",
        "data_read_per_join": "24K"
      },
      "used_columns": [
        "feature_id",
        "product_id",
        "variant_id",
        "lang_code"
      ],
      "attached_condition": "((`test2_gaseus`.`cscart_product_features_values`.`product_id` in (13014,13015,13016,13017,13018,13019,13020,13021,13022,13023,13024,13025,13026,13027)) and (`test2_gaseus`.`cscart_product_features_values`.`feature_id` in (646,647,595,628,627,624,625,553,626,622,623,636,637)) and (`test2_gaseus`.`cscart_product_features_values`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id feature_id variant_id
13014 553 1973
13015 553 1973
13016 553 1973
13017 553 1973
13018 553 1973
13019 553 1973
13020 553 1973
13021 553 1973
13022 553 1973
13023 553 1973
13024 553 1973
13025 553 1973
13026 553 1973
13027 553 1973
13014 595 1904
13015 595 1904
13016 595 1905
13017 595 1905
13018 595 1789
13019 595 1789
13020 595 2499
13021 595 2499
13022 595 1787
13023 595 1787
13024 595 1900
13025 595 1900
13026 595 1899
13027 595 1899
13014 622 2497
13015 622 2497
13016 622 2497
13017 622 2497
13018 622 2497
13019 622 2497
13020 622 2497
13021 622 2497
13022 622 2497
13023 622 2497
13024 622 2497
13025 622 2497
13026 622 2497
13027 622 2497
13014 623 2501
13015 623 2501
13016 623 2501
13017 623 2501
13018 623 2501
13019 623 2501
13020 623 2501
13021 623 2501
13022 623 2501
13023 623 2501
13024 623 2501
13025 623 2501
13026 623 2501
13027 623 2501
13014 624 1803
13015 624 1803
13016 624 1803
13017 624 1803
13018 624 1803
13019 624 1803
13020 624 1803
13021 624 1803
13022 624 1803
13023 624 1803
13024 624 1803
13025 624 1803
13026 624 1803
13027 624 1803
13014 625 2513
13015 625 2513
13016 625 2513
13017 625 2513
13018 625 2513
13019 625 2513
13020 625 2513
13021 625 2513
13022 625 2513
13023 625 2513
13024 625 2513
13025 625 2513
13026 625 2513
13027 625 2513
13014 626 2031
13015 626 2031
13016 626 2031
13017 626 2031
13018 626 2031
13019 626 2031
13020 626 2031
13021 626 2031
13022 626 2031
13023 626 2031
13024 626 2031
13025 626 2031
13026 626 2031
13027 626 2031
13014 627 1659
13015 627 1659
13016 627 1659
13017 627 1659
13018 627 1659
13019 627 1659
13020 627 1659
13021 627 1659
13022 627 1659
13023 627 1659
13024 627 1659
13025 627 1659
13026 627 1659
13027 627 1659
13014 628 1660
13015 628 1660
13016 628 1660
13017 628 1660
13018 628 1660
13019 628 1660
13020 628 1660
13021 628 1660
13022 628 1660
13023 628 1660
13024 628 1660
13025 628 1660
13026 628 1660
13027 628 1660
13014 636 2348
13015 636 2348
13016 636 2348
13017 636 2348
13018 636 2348
13019 636 2348
13020 636 2348
13021 636 2348
13022 636 2348
13023 636 2348
13024 636 2348
13025 636 2348
13026 636 2348
13027 636 2348
13014 637 2345
13015 637 2345
13016 637 2345
13017 637 2345
13018 637 2345
13019 637 2345
13020 637 2345
13021 637 2345
13022 637 2345
13023 637 2345
13024 637 2345
13025 637 2345
13026 637 2345
13027 637 2345
13014 646 2369
13015 646 2370
13016 646 2369
13017 646 2370
13018 646 2369
13019 646 2370
13020 646 2369
13021 646 2370
13022 646 2369
13023 646 2370
13024 646 2369
13025 646 2370
13026 646 2369
13027 646 2370
13014 647 2373
13015 647 2374
13016 647 2373
13017 647 2374
13018 647 2373
13019 647 2374
13020 647 2373
13021 647 2374
13022 647 2373
13023 647 2374
13024 647 2373
13025 647 2374
13026 647 2373
13027 647 2374