SELECT 
  cscart_products.* 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    376, 1612, 1613, 1614, 1615, 1616, 1617, 
    1618, 5476, 5473, 1843, 1841, 1840, 
    486, 1842
  )

Query time 0.00054

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": 15,
      "filtered": 100,
      "index_condition": "cscart_products.product_id in (376,1612,1613,1614,1615,1616,1617,1618,5476,5473,1843,1841,1840,486,1842)"
    }
  }
}