Sandbox

SELECT 
  1 
FROM 
  cscart_aprilec_print_temp_designs 
WHERE 
  session_id = 'TRUE-8N57-1UWM-P2VK-O4UR-FRNF-9K1M-D855' 
  AND product_id = 239 
  AND expires_at > 1777141183 
  AND confirmed = 'Y' 
LIMIT 
  1

Query time 0.00028

JSON explain

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