Recently I am doing an investigation for creating a multiple tier application. Every topic that I have read suggests that the 3-tier architecture is better than the 2-tier architecture because by exposing the connection string of the database at the client side you create a big security hole at your system. All of these articles just explains that it is a bad idea to expose the location of the database and none of them explains why.
Can anybody help me and explain to me the threads of exposing the location of the database? I mean they will know the location but they will not know the username and the password in order to log in and to modify the database. What make the 3-tier architecture more safe than the 2-tier architecture? Is it only the extra hope in order to reach the database?
Thanks in advance, Constantin Patak
The connection string includes the username and password. If your client application can hit the database directly, then the user can inspect the client application and extract the connection credentials to do the same.
The middle tier will provide APIs which correspond to the operations you want clients to be able to perform. The client is shielded from the internal implementation which may or may not include a database. You will be able to change the implementation without affecting the client. Perhaps you will find that the load is so high you need to switch from RDS to NoSQL. The client doesn't need to know or change. Perhaps you will start caching some results without hitting your database. Again, the client doesn't need to know or change. This is why the industry has standardized around not hitting the database directly from client applications.