SQL server 2012 CPU usage spikes to 100%

I am using MSSQL server 2014 in AWS and the AWS image configuration is 4 cores and 16 GB RAM(m3.xlarge). I am running the following simple query,

select * from user_table where user_id = '10'

user_table contains 1000k records, user_id is primary key. When the above simple query is executed from my application through EJB hibernate, the CPU spikes to 10% for a moment and again it backs to normal.

So my use case is, 100 users will concurrently try to hit the application, so in a fraction of second 100 times the above query will try to execute in a fraction of second. So the CPU usage spikes to 100%. Once all the query execution is completed the CPU usage is back to normal at 1%.

• Why it so? whether I need to increase my AWS instance type?
• What should I have to do in-order to make SQL server to handle 100 or more concurrent hits without making high CPU usage? If my query is so complex then there might have a chance to get spike but my query is simple and straight forward.
• Is there is any bench mark metrics available for SQL server 2014?
• Any solution to make support for concurrent hits with SQL server by low CPU usage consumption?