In SambaPOS the machine with SQL server installed is doing the work - at least for the database query part. There will be some processing done in the SambaPOS software as well.
Regarding what I was meaning with a web server, for SQL traffic - the web server has received a query from the end user, it then processes the request and part of that will involve sending queries to SQL server. SQL server then returns the results of those queries to the web server. The web server then puts together the html to deliver back to the end user’s browser.
So that is where it is different from SambaPOS. In the most simple web server setup (I am not talking about large scale websites across multiple servers), you have a web server (software) like IIS, Apache, etc., and a database server like SQL Server, MySQL, etc. Both can be on the same machine. So you can consider a typical website is like a single terminal setup for SambaPOS - the SQL traffic is between the web server and SQL Server - the web server is like SambaPOS, the software. All your web traffic is irrelevant because the SQL traffic is done on the server between the web server and SQL server. You can have 1,000 visitors to your website from all around the world, but those hit the web server only, they never talk to SQL server directly (if they did, that would be a huge security risk). So the visitors to the website are irrelevant - the SQL traffic is only between the web server and SQL server.
That’s why I say SambaPOS is different - because in a multi terminal setup, you can have multiple machines running SambaPOS and they all individually communicate with SQL server.
SambaPOS will be doing the JSON processing regardless - this has nothing to do with JSON support in SQL Server. To be specific, it is more than likely Entity Framework is doing the JSON processing. But yes, generally, that processing is then being done on the client side which will be the RDP host machine in this case.
You are referring to JSON query support here, which was introduced in SQL Server 2016. I am pretty sure SambaPOS won’t utilise that as, if it did, would mean it has to access data from SQL Server 2014 and earlier differently, and that would be a pain to manage. Now, Entity Framework may however do something differently, but that is separate from SambaPOS (almost like “hidden”).
When we do custom scripts or want to get data from the JSON fields via SQL, we can utilise the JSON query support in SQL Server 2016 and above, but AFAIK that is only ever when it gets used in SambaPOS - in the scripts we make.