Sandbox

SELECT 
  1 
FROM 
  cscart_aprilec_print_temp_designs 
WHERE 
  session_id = '950M-E1K4-E7I5-K1CK-G41U-S14A-MK4A-L6HE' 
  AND product_id = 136 
  AND expires_at > 1777137165 
  AND confirmed = 'Y' 
LIMIT 
  1

Query time 0.00030

JSON explain

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