Is it generally fast enough to make simple updates synchronously? For instance with a ASP.NET web app, if I change the person's name... will I have any issues just updating the index synchronously as part of the "Save" mechanism?
OR is the only safe way to have some other asynchronous process to make the index updates?
We do updates both synchronous and asynchronously depending on the kind of action the user is doing. We have implemented the synchronous indexing in a way where we use the asynchronous code and just waits for some time for its completion. We only wait for 2 seconds which means that if it takes longer then the user will not see the update but normally the user will.
We configured logging in a way so we would get notified whenever the "synchronous" indexing took longer than we waited to get an idea of how often it would happen. We hardly ever get over the 2 second limit.
If you are using full text session, then you don't need to update indexs explicitly. full text session take care of indexing updated entity.