Monolithic applications are easy to monitor. In a monolithic application, there are fewer points to monitor as it is one service(big fat war). Points to monitor would include the database service, disk spaces, CPUs usage, any third-party tools and so on. Monitoring effort in microservices architecture increases exponentially. Each service requires the same number of points to monitor as normally found in one monolithic application. Imagine the alert rate when microservices numbers keep increasing in 100s. Monitoring and self-healing tools/script such as Nagios and Monit should be in place to handle and react to alerts coming from different services.