SELECT 
  product_id, 
  feature_id, 
  variant_id 
FROM 
  cscart_product_features_values 
WHERE 
  product_id IN (
    7108, 7109, 7224, 7225, 7246, 7245, 7268, 
    7267, 7271, 7270, 6844, 6854, 3307, 
    6864, 6860, 6855, 3317, 3313, 3862, 
    3315
  ) 
  AND feature_id IN (
    628, 595, 641, 637, 636, 627, 623, 622, 
    626, 553, 625, 624
  ) 
  AND lang_code = 'en'

Query time 0.00698

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "54.33"
    },
    "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": "idx_product_feature_variant_id",
      "used_key_parts": [
        "product_id",
        "feature_id",
        "lang_code"
      ],
      "key_length": "12",
      "rows_examined_per_scan": 240,
      "rows_produced_per_join": 240,
      "filtered": "100.00",
      "using_index": true,
      "cost_info": {
        "read_cost": "30.33",
        "eval_cost": "24.00",
        "prefix_cost": "54.33",
        "data_read_per_join": "185K"
      },
      "used_columns": [
        "feature_id",
        "product_id",
        "variant_id",
        "lang_code"
      ],
      "attached_condition": "((`gaseus`.`cscart_product_features_values`.`product_id` in (7108,7109,7224,7225,7246,7245,7268,7267,7271,7270,6844,6854,3307,6864,6860,6855,3317,3313,3862,3315)) and (`gaseus`.`cscart_product_features_values`.`feature_id` in (628,595,641,637,636,627,623,622,626,553,625,624)) and (`gaseus`.`cscart_product_features_values`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id feature_id variant_id
3307 553 1973
3307 595 1789
3307 622 2325
3307 623 1975
3307 624 1705
3307 625 2351
3307 626 2343
3307 627 1659
3307 628 1712
3307 636 2344
3307 637 2345
3307 641 2347
3313 553 1973
3313 595 2075
3313 622 1937
3313 623 1983
3313 624 1705
3313 625 2137
3313 626 2343
3313 627 1659
3313 628 1712
3313 636 2344
3313 637 2345
3313 641 2347
3315 553 1973
3315 595 1941
3315 622 1942
3315 623 1983
3315 624 1705
3315 625 2341
3315 626 2343
3315 627 1659
3315 628 1712
3315 636 2344
3315 637 2345
3315 641 2347
3317 553 1973
3317 595 1905
3317 622 1946
3317 623 1975
3317 624 1705
3317 625 2137
3317 626 2343
3317 627 1659
3317 628 1712
3317 636 2344
3317 637 2345
3317 641 2347
3862 553 1973
3862 595 1902
3862 622 2325
3862 623 1983
3862 624 1694
3862 625 2137
3862 626 2343
3862 627 1659
3862 628 1712
3862 636 2344
3862 637 2345
3862 641 2347
6844 553 1973
6844 595 1787
6844 622 2325
6844 623 1975
6844 624 1705
6844 625 2341
6844 626 2343
6844 627 1659
6844 628 1712
6844 636 2344
6844 637 2345
6844 641 2347
6854 553 1973
6854 595 1787
6854 622 2325
6854 623 1975
6854 624 1705
6854 625 2351
6854 626 2343
6854 627 1659
6854 628 1712
6854 636 2344
6854 637 2345
6854 641 2347
6855 553 1973
6855 595 1789
6855 622 2325
6855 623 1975
6855 624 1705
6855 625 2137
6855 626 2343
6855 627 1659
6855 628 1712
6855 636 2344
6855 637 2345
6855 641 2347
6860 553 1973
6860 595 2075
6860 622 1937
6860 623 1983
6860 624 1705
6860 625 2351
6860 626 2343
6860 627 1659
6860 628 1712
6860 636 2344
6860 637 2345
6860 641 2347
6864 553 1973
6864 595 1905
6864 622 1946
6864 623 1975
6864 624 1705
6864 625 2351
6864 626 2343
6864 627 1659
6864 628 1712
6864 636 2344
6864 637 2345
6864 641 2347
7108 553 1973
7108 595 1748
7108 622 2325
7108 623 1975
7108 624 1705
7108 625 2137
7108 626 2343
7108 627 1659
7108 628 1712
7108 636 2344
7108 637 2345
7108 641 2347
7109 553 1973
7109 595 1748
7109 622 2325
7109 623 1975
7109 624 1705
7109 625 2138
7109 626 2343
7109 627 1659
7109 628 1712
7109 636 2344
7109 637 2345
7109 641 2347
7224 553 1973
7224 595 2000
7224 622 1937
7224 623 1983
7224 624 1705
7224 625 2137
7224 626 2343
7224 627 1659
7224 628 1712
7224 636 2344
7224 637 2345
7224 641 2347
7225 553 1973
7225 595 2000
7225 622 1937
7225 623 1983
7225 624 1705
7225 625 2138
7225 626 2343
7225 627 1659
7225 628 1712
7225 636 2344
7225 637 2345
7225 641 2347
7245 553 1973
7245 595 1995
7245 622 1937
7245 623 1983
7245 624 1705
7245 625 2137
7245 626 2343
7245 627 1659
7245 628 1712
7245 636 2344
7245 637 2345
7245 641 2347
7246 553 1973
7246 595 1995
7246 622 1937
7246 623 1983
7246 624 1705
7246 625 2138
7246 626 2343
7246 627 1659
7246 628 1712
7246 636 2344
7246 637 2345
7246 641 2347
7267 553 1973
7267 595 1902
7267 622 1937
7267 623 1983
7267 624 1705
7267 625 2137
7267 626 2343
7267 627 1659
7267 628 1712
7267 636 2344
7267 637 2345
7267 641 2347
7268 553 1973
7268 595 1902
7268 622 1937
7268 623 1983
7268 624 1705
7268 625 2138
7268 626 2343
7268 627 1659
7268 628 1712
7268 636 2344
7268 637 2345
7268 641 2347
7270 553 1973
7270 595 1900
7270 622 1937
7270 623 1983
7270 624 1705
7270 625 2137
7270 626 2343
7270 627 1659
7270 628 1712
7270 636 2344
7270 637 2345
7270 641 2347
7271 553 1973
7271 595 1900
7271 622 1937
7271 623 1983
7271 624 1705
7271 625 2138
7271 626 2343
7271 627 1659
7271 628 1712
7271 636 2344
7271 637 2345
7271 641 2347