SELECT 
  cscart_products.* 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    12995, 12996, 12997, 12998, 15744, 15745, 
    15746, 15743, 15738, 15739, 15740, 
    15741, 15742, 15736, 15737, 12999, 
    13000, 13001, 13002, 13003
  )

Query time 0.00065

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 (12995,12996,12997,12998,15744,15745,15746,15743,15738,15739,15740,15741,15742,15736,15737,12999,13000,13001,13002,13003)"
    }
  }
}