SELECT 
  1 
FROM 
  cscart_ec_print_temp_designs 
WHERE 
  session_id = 'K5A9-53NY-IVP8-7TNJ-0QG4-2Y5K-BFVH-CK38' 
  AND product_id = 206 
  AND expires_at > 1770526528 
  AND confirmed = 'Y' 
LIMIT 
  1

Query time 0.00035

JSON explain

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