SELECT 
  cscart_products.* 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    643, 642, 641, 645, 507, 814, 815, 218, 
    1119, 1120, 1121, 861, 859, 437, 428, 
    843, 862, 1108, 267, 857, 1749, 396, 
    1659, 791
  )

Query time 0.00143

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": 24,
      "filtered": 100,
      "index_condition": "cscart_products.product_id in (643,642,641,645,507,814,815,218,1119,1120,1121,861,859,437,428,843,862,1108,267,857,1749,396,1659,791)"
    }
  }
}