SELECT 
  cscart_products.* 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    12838, 12853, 12854, 12855, 12856, 12857, 
    12858, 12859, 12860, 12861, 12862, 
    12863, 12864, 12865, 12866, 12867, 
    12873, 12872, 12875, 12871
  )

Query time 0.00056

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_products",
      "access_type": "range",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["product_id"],
      "rows": 20,
      "filtered": 100,
      "index_condition": "cscart_products.product_id in (12838,12853,12854,12855,12856,12857,12858,12859,12860,12861,12862,12863,12864,12865,12866,12867,12873,12872,12875,12871)"
    }
  }
}