Sandbox

SELECT 
  1 
FROM 
  cscart_ec_print_temp_designs 
WHERE 
  session_id = '11GD-MBZT-E9F2-W92G-9IMO-YTN8-Z8CH-KLNY' 
  AND product_id = 18 
  AND expires_at > 1770174755 
  AND confirmed = 'Y' 
LIMIT 
  1

Query time 0.00029

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}