SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e4ae4f5361c15b1d7d019f500c02f2f613d4338939f0decd8addf59099b05dc8' 
  AND token = 'j8BmqIaoMwq+I/wGBWTQtWhZ3hPDyYLHjqmOi1gm+RQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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