Sandbox

SELECT 
  1 
FROM 
  cscart_ec_print_temp_designs 
WHERE 
  session_id = '7VEY-9QI9-72BA-O2KK-18V2-SVIZ-U4C8-TST9' 
  AND product_id = 121 
  AND expires_at > 1770174843 
  AND confirmed = 'Y' 
LIMIT 
  1

Query time 0.00025

JSON explain

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