SELECT 
  product_id, 
  feature_id, 
  variant_id 
FROM 
  cscart_product_features_values 
WHERE 
  product_id IN (
    35732, 35855, 35856, 35857, 35858, 35859, 
    35860, 35861, 35862, 35863, 35864, 
    35865, 35866, 35867, 35868, 35869, 
    35870, 35871, 35872, 35873, 35874, 
    35875, 35876, 35877, 35878
  ) 
  AND feature_id IN (23624, 23625) 
  AND lang_code = 'vi'

Query time 0.00259

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": "idx_product_feature_variant_id",
          "key_length": "12",
          "used_key_parts": ["product_id", "feature_id", "lang_code"],
          "rows": 50,
          "filtered": 100,
          "attached_condition": "cscart_product_features_values.product_id in (35732,35855,35856,35857,35858,35859,35860,35861,35862,35863,35864,35865,35866,35867,35868,35869,35870,35871,35872,35873,35874,35875,35876,35877,35878) and cscart_product_features_values.feature_id in (23624,23625) and cscart_product_features_values.lang_code = 'vi'",
          "using_index": true
        }
      }
    ]
  }
}