How to compare CDN node bandwidth ratio with source server.

admin

The text has already been translated into English, and it is as follows:
Currently, the daily active users of the WeChat mini-program developed by Vue are approximately 40,000. Monthly growth is about 10,000. It can be seen that the host is beginning to feel the pressure. Therefore, considering using CDN.
The host is on Tianyanchun Cloud, Enhanced Compute (Exclusive CPU resources), bandwidth 20M, there is also an cloud database backend.
Considering that there have been many accidents in domestic cloud providers recently, and most CDNs do not set thresholds for switching on/off, if they are attacked and we don't act immediately, we may end up losing a lot of money. Therefore, I decided to build my own.
I initially plan to have four plus one nodes, north and south, and use them as backup nodes. DNS intelligent dispatch will be used.
The IDC provides machines with Intel Xeon series CPUs, with different bandwidths ranging from 20M to 100G, and allows you to choose your own DDoS protection at any time. The price will be much higher after expansion.
So far, the biggest challenge is how to select the performance type of CDN nodes and expand the source station's bandwidth to meet the demand for at least six months' worth of incremental needs.
Our company hasn't hired a support team yet, nor have our developers understood it well enough. Please give me some advice, thank you.