I think the capacity of AWS EC2 t2.micro instance is too low. I was sending somewhere around 100 mails to the customers and we had some 20+ users online. And the instance crashed. I had to restart it and it took around 10 mins to get it back working.
When i checked the monitoring it said the CPU utilization was just 2% and no other indications shown any overload.
What do you think he issue is? How can i prevent this happening in future?
I think the capacity of AWS EC2 t2.micro instance is too low.
Perhaps it's too low for your application. I ensure you, AWS has provisioned t2.micro instances exactly how they want. Keep in mind, you're getting this for free, and this is most definitely an area where you get what you pay for.
t2.micro instances are really only good for the most minimal test/dev scenarios, or offline batch processing type tasks where all load is asynchronous and interactivity is non-existent.
CPU is only one of many resources that could have contributed to your "crash". Memory, network I/O, disk I/O could have also played a role. To determine if your load has outgrown the t2.micro, you'll need to set up some type of resource monitoring system, and then use that to identify areas of resource contention.
If you don't have the time or skills to do that, though, just upgrade to a larger instance.
Aside from the fact that you really shouldn't be expecting much from a micro instance given you for free... if it actually crashed instead of simply being too slow, then something is probably broken in your application and/or configuration.
