SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '831d7ad3ccc63bc9c3f47dc52afb7c7bb975b3e2bef8c8abd035dbfe8e635b21' 
  AND token = 'lsR/FvfSrA0JfLzGGXuUJKR+HAPAhBFNa0/JoYkCjHs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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