Sandbox

SELECT 
  1 
FROM 
  cscart_ec_print_temp_designs 
WHERE 
  session_id = 'QVVS-7ZN2-SZDC-OAR2-WQD8-MIM4-KDY6-AUH4' 
  AND product_id = 18 
  AND expires_at > 1771080926 
  AND confirmed = 'Y' 
LIMIT 
  1

Query time 0.00040

JSON explain

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