Sandbox

SELECT 
  1 
FROM 
  cscart_june_setupec_print_temp_designs 
WHERE 
  session_id = 'P4CE-SMGR-U7BN-86U6-GN2F-X0S5-1JJ0-EQON' 
  AND product_id = 21 
  AND expires_at > 1781893746 
  AND confirmed = 'Y' 
LIMIT 
  1

Query time 0.00034

JSON explain

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