5.4. Do you need a Database?

• Paul Graham wrote in his ViaWeb FAQ, that he did not use a database for ViaWeb (now Yahoo Store):

• We didn't use one. We just stored everything in files. The Unix file system is pretty good at not losing your data, especially if you put the files on a Netapp.

  It is a common mistake to think of Web-based apps as interfaces to databases. Desktop apps aren't just interfaces to databases; why should Web-based apps be any different? The hard part is not where you store the data, but what the software does.

• I disagree with this statement.
• Desktop apps don't always use databases, because they can afford to load the data on start-up, store it internally in memory using efficient data-structures, and then saving the data to disk serialized, at an Exit or a Save command.
• Web-based programs, on the other hand, cannot afford to load and store the serialized data during every web-request done, and cannot maintain a state in memory because the HTTP protocol is stateless.
• A database system allows them to manipulate efficient and complex data structures without having to constantly serialize and de-serialize them.
• It is also probable that when working against the raw file-system, one will implement a lot of database functionality using the file-system primitives, which may be a lot of extra work.
• See for instance Subversion's libsvn_fs_fs