rest - Maximum number of record returned by the server. Why 1000?

Why in AGS "maximum number of record returned by the server" is set to default 1000?

What happens if I increase limit to 100000 or 1000000 in 100 services?

Answer

It's a combination of two things really. 1) How much information can your server handle sending at a given time. 2) How much information can your client handle displaying.

I can't answer "why" 1000. A good a guess as any, 1000 individual features drawn on a webmap would really tax the web browser and performance would suffer (a few years back). You can make the argument now that browsers can handle 1000+.

But to use your example, do the quick math. Say you had 100 services. Each service could return 100,000 features. Each feature has 10 attributes. Then make a max request for each service all at the same time. Will the Server/hardware handle that? Will your web server be able to transfer that much data? Is your internet connection fast enough to handle it?

I'd call 1000 a "protective" number. Increase it to what makes sense in your environment as long as you understand the limits of both your Server and Client.