SELECT 
  product_id, 
  feature_id, 
  variant_id 
FROM 
  cscart_product_features_values 
WHERE 
  product_id IN (
    12885, 12886, 12887, 12888, 12889, 12890, 
    12891, 12892, 12893, 12894, 12895, 
    12876, 12877, 12878, 12879, 12880, 
    12881, 12882, 12883, 12884
  ) 
  AND feature_id IN (
    637, 636, 623, 622, 626, 553, 625, 624, 
    627, 628, 595
  ) 
  AND lang_code = 'en'

Query time 0.00542

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "8.38"
    },
    "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": 22,
      "rows_produced_per_join": 22,
      "filtered": "100.00",
      "using_index_for_skip_scan": true,
      "cost_info": {
        "read_cost": "6.18",
        "eval_cost": "2.20",
        "prefix_cost": "8.38",
        "data_read_per_join": "17K"
      },
      "used_columns": [
        "feature_id",
        "product_id",
        "variant_id",
        "lang_code"
      ],
      "attached_condition": "((`test2_gaseus`.`cscart_product_features_values`.`product_id` in (12885,12886,12887,12888,12889,12890,12891,12892,12893,12894,12895,12876,12877,12878,12879,12880,12881,12882,12883,12884)) and (`test2_gaseus`.`cscart_product_features_values`.`feature_id` in (637,636,623,622,626,553,625,624,627,628,595)) and (`test2_gaseus`.`cscart_product_features_values`.`lang_code` = 'en'))"
    }
  }
}