SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b56a223e78013ebfb2203358bb2aff477a0e9d611674c5b12d1271ffa06a387' 
  AND token = 'XKF5lMxw+VKPSTtWJIEp9tsUWmWtDGa0vH6hQB+K+Nw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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