SELECT 
  product_id, 
  feature_id, 
  variant_id 
FROM 
  cscart_product_features_values 
WHERE 
  product_id IN (
    49868, 49867, 49864, 49865, 49866, 49873, 
    49872, 49871, 49870, 49869, 40818, 
    49874, 49875, 49876
  ) 
  AND feature_id IN (24144, 25095) 
  AND lang_code = 'vi'

Query time 0.00467

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": 44,
          "filtered": 95.45454407,
          "attached_condition": "cscart_product_features_values.product_id in (49868,49867,49864,49865,49866,49873,49872,49871,49870,49869,40818,49874,49875,49876) and cscart_product_features_values.feature_id in (24144,25095) and cscart_product_features_values.lang_code = 'vi'",
          "using_index": true
        }
      }
    ]
  }
}