SELECT 
  cscart_products.* 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    939, 937, 938, 940, 946, 936, 947, 942, 
    951, 941, 945, 944, 948, 952
  )

Query time 0.00038

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": 14,
      "filtered": 100,
      "index_condition": "cscart_products.product_id in (939,937,938,940,946,936,947,942,951,941,945,944,948,952)"
    }
  }
}