Thousands of users with FM8SA IWP

[SJM]

Dear FM Forums,

One of the main reasons we want to use Instant Web Publishing is so that we can have a vendor portal. We have thousands of vendors, and we'd like to have an interface where they can login and update some of their information. What are the options for using IWP to give limited access to thousands of users, only a few of which will ever access at a given time, and none of which will ever access the FileMaker solution directly?

At first glance, there would seem to be two options: make a FileMaker Account for each vendor that will access the system, or make a generic account that all vendors login with, and implement within the solution a custom set of credentials for each vendor, which they have to provide immediately after giving the generic vendor login and before they can see or modify their own record.

For the first option, are there any limits to the number of FileMaker accounts that can be made for one file, or any performance problems in a solution with, say, 2000 accounts?

For the second option, is there any conflict if two (or a thousand) different browsers try to start simultaneous sessions with the same FileMaker account login?

Are there any other well-known approaches to this situation?

Also, what are people's experiences with IWP in general? Is it robust? Does it choke the web browser when using legacy layouts imported from FileMaker 6 (random example)? Does it work largely as advertised? (I'd assume yes based on my experience with FileMaker products to date.)

Thank you for any insight or advice!