Instance Type to Use

Question

Hello,

I am currently using a T3 small instance with 2 vcpu and 2 GB ram for a school web application (LAMP) . It is working fine and handles the load well.
I wish to replicate the web app for 4 other schools.

I thus want to upgrade the same instance to cater for the need. 
When I checked the price calculator for 2 VPUs and 16 GB Ram, it recommends me a r6g.large instance. I am just wondering why propose r6g type when there is t3.xlarge with almost the same spec. Am i missing something here?

I believe there could be a max of 5000 users per day accessing the web app during school hours. Traffic during school holidays (2 months per year) would be very low (maybe 200 users per day)

Answer

t3.xlarge offers 4 vCPU and 16GB RAM while r6g.large offers 2 vCPU and 16GB RAM ie. r6g instance offers more memory ratio. Also t3x.xlarge is burstable instance which means that the performance is limited to sustain at around 20-30%, anything more than that it will need to consume burst credit.

Usually to estimate whether your current capacity is sufficient, you would need to do a load test. The maximum instance capacity is usually limited to a number of users it can handle concurrently (ex: 100 users concurrent or per second). So although 1 day the school can have max 5000 students, you still need to know how many out of 5000 may access the web app concurrently. It is probably much less unless it is exam period.

Instance Type to Use

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