SELECT 
  product_id, 
  feature_id, 
  variant_id 
FROM 
  cscart_product_features_values 
WHERE 
  product_id IN (
    13212, 13213, 13214, 13215, 13216, 13217, 
    13211
  ) 
  AND feature_id IN (
    637, 636, 647, 646, 623, 622, 626, 553, 
    625, 624, 627, 628, 595
  ) 
  AND lang_code = 'en'

Query time 0.00814

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "6.75"
    },
    "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": 16,
      "rows_produced_per_join": 16,
      "filtered": "100.00",
      "using_index_for_skip_scan": true,
      "cost_info": {
        "read_cost": "5.15",
        "eval_cost": "1.60",
        "prefix_cost": "6.75",
        "data_read_per_join": "12K"
      },
      "used_columns": [
        "feature_id",
        "product_id",
        "variant_id",
        "lang_code"
      ],
      "attached_condition": "((`test2_gaseus`.`cscart_product_features_values`.`product_id` in (13212,13213,13214,13215,13216,13217,13211)) and (`test2_gaseus`.`cscart_product_features_values`.`feature_id` in (637,636,647,646,623,622,626,553,625,624,627,628,595)) and (`test2_gaseus`.`cscart_product_features_values`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id feature_id variant_id
13211 553 1973
13212 553 1973
13213 553 1973
13214 553 1973
13215 553 1973
13216 553 1973
13217 553 1973
13211 595 1904
13212 595 1905
13213 595 1789
13214 595 2499
13215 595 1787
13216 595 1900
13217 595 1899
13211 622 2497
13212 622 2497
13213 622 2497
13214 622 2497
13215 622 2497
13216 622 2497
13217 622 2497
13211 623 2501
13212 623 2501
13213 623 2501
13214 623 2501
13215 623 2501
13216 623 2501
13217 623 2501
13211 624 1803
13212 624 1803
13213 624 1803
13214 624 1803
13215 624 1803
13216 624 1803
13217 624 1803
13211 625 2147
13212 625 2147
13213 625 2147
13214 625 2147
13215 625 2147
13216 625 2147
13217 625 2147
13211 626 1829
13212 626 1829
13213 626 1829
13214 626 1829
13215 626 1829
13216 626 1829
13217 626 1829
13211 627 1659
13212 627 1659
13213 627 1659
13214 627 1659
13215 627 1659
13216 627 1659
13217 627 1659
13211 628 1660
13212 628 1660
13213 628 1660
13214 628 1660
13215 628 1660
13216 628 1660
13217 628 1660
13211 636 2348
13212 636 2348
13213 636 2348
13214 636 2348
13215 636 2348
13216 636 2348
13217 636 2348
13211 637 2345
13212 637 2345
13213 637 2345
13214 637 2345
13215 637 2345
13216 637 2345
13217 637 2345
13211 646 2370
13212 646 2370
13213 646 2370
13214 646 2370
13215 646 2370
13216 646 2370
13217 646 2370
13211 647 2374
13212 647 2374
13213 647 2374
13214 647 2374
13215 647 2374
13216 647 2374
13217 647 2374