Is it possible to build a custom customer portal that access Salesforce data without a user? For example: the portal would be a web app written form scratch, and it would communicate with Salesforce through APIs.
Can this be done without registered users on the org, while keeping a good authentication for the API?
What I mean by this is that the web app would need to authenticate with Salesforce when making requests, but I would like to do this without using Salesforce user credentials.
I know that this could be done with the web app using credentials/tokens that can be analyzed at the beginning of the API request handling with Apex, but I'm not sure if this is secure enough.
If there is another way of doing this, I would like to know.
The context is that I want to create a portal for specific customers, so they would be able to see/track orders, for example. I'm not sure of how many users from these customer companies would use the app (hence the need for not using Salesforce licenses, because they are too expensive for this situation).
Also, Salesforce has a limit of 100 communities per org, so if I get more than 100 customers that use this service, Salesforce would not be able to provide what I need.
At the end I need an individual customer portal, since each customer has different needs.