SELECT 
  product_id, 
  feature_id, 
  variant_id 
FROM 
  cscart_product_features_values 
WHERE 
  product_id IN (
    44878, 45056, 45057, 45058, 45059, 45060, 
    45061, 45062, 45063, 45064
  ) 
  AND feature_id IN (24559) 
  AND lang_code = 'vi'

Query time 0.00169

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "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",
          "key_length": "6",
          "used_key_parts": ["feature_id", "product_id"],
          "rows": 20,
          "filtered": 55,
          "attached_condition": "cscart_product_features_values.feature_id = 24559 and cscart_product_features_values.product_id in (44878,45056,45057,45058,45059,45060,45061,45062,45063,45064) and cscart_product_features_values.lang_code = 'vi'",
          "using_index": true
        }
      }
    ]
  }
}

Result

product_id feature_id variant_id
44878 24559 85672
45056 24559 85681
45057 24559 85673
45058 24559 85674
45059 24559 85675
45060 24559 85676
45061 24559 85677
45062 24559 85678
45063 24559 85679
45064 24559 85680