Thinking about performance issues. How many concurrent connections can a server code script support? What does it depend upon?
It depends what plan you have, details about emConcurrent Scripts/em you can find on our page in the section below: https://appery.io/pricing
I believe you are still limited to the burst rate for your plan. So if the burst rate is 5 calls per second, you can have up to 5 calls running at the same time. If you reach the limit in the scripts, this could lock up connections for others that are currently using the app.
You can do a simple test in the Server Code to make 10 concurrent calls, and console.log each result. This would verify the limitation.
I have 3 calls/sec limitation
how reasonable is a limit of 3 calls /sec in real life?
If 3 calls per second is not enough for you, you may upgrade your plan or make request for the Enterprise plan and ask for condition you need.