There is no connection open to the database, so we cannot lock record(s) to avoid concurrency problems. If we had the connection, we can limit concurrency with exclusive access to that record.
So, we need to deal with optimistic concurrency. Create a snapshot of the records (marked as original records); change data with the client application; then send it back to the Web. What could happen? If another user performs the same operations at the same time, starting from the same copy of the data, the application can do two things: