SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a9b492023d12e45b4e84b486b3fde82ca7487685b75d543fdc8adeea37b9156f' 
  AND token = 'l/hlawvfhpy9eBOMjMKNcRrZDK5BAJ7z9uDnNLE81Io=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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