SELECT 
  1 
FROM 
  cscart_aprilec_print_temp_designs 
WHERE 
  session_id = '6CRN-KZJ7-VH5Z-D3NX-KDLR-C1ZA-JYAS-1HYH' 
  AND product_id = 81 
  AND expires_at > 1777133773 
  AND confirmed = 'Y' 
LIMIT 
  1

Query time 0.00036

JSON explain

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