2,000,000,000,000 WordPress posts, is it possible?

Simple answer, Yes. The days of 2GB size limit on file systems are gone. Now, you can literally have unlimited entries on almost everywhere if your hardware can support it. So I’m gonna change the question into this:

2,000,000 WordPress posts, Should I have it?

To decide whether WordPress is a good choice for such projects, you have to note a few things here:

1- Uploads

If your posts are going to have images, then this is where you might have a problem. considering the default thumbnail sizes of every image (thumbnail, medium, medium-large, large + the image itself), you will end up having at least 5 generated image for each post (assuming each post only has 1 image). This means you will end up having 10,000,000 images, and if you not choose to organize your uploads, well then, trouble gets closer.

Although you can have 4,294,967,295 (2³² -1) files in a folder even on a NTFS partition (the actual limitation is lower), but having drastic decreased performance while listing 10 million files is inevitable. So I suggest you should use a upload organizer plugin in this case.

2- Database entries

Databases can also contain massive number of rows and huge size of entries. A MyISAM storage engine supports 2³² rows per table, which is far far more than what average websites need.

WordPress creates entries other than the original post itself in the database. Each post can have unlimited meta attached to it, limited by the database itself. So if your posts are going to have a lot of meta data (Images, Custom fields, etc) then doing a heavy task such as a complicated meta query is gonna take considerable time and resources.

It is worth mentioning that you should clean up your database once in a while, to avoid unwanted performance decrease. You can either optimize it using scripts such as PHPMyAdmin or by using WordPress plugins.

Conclusion

WordPress itself is not the most optimized platform. If you do a quick search, you’ll notice there are a lot of questions about decreased performance when it comes to thousands and tens of thousand of posts.

So, again it’s up to you to decide if this platform is suitable for you or not. There are a lot of scripts already made for this. A quick search about RSS Aggregator can lead you to endless result on this. You might as well find it best to have your own script written, for a couple of thousand dollars, if you are going commercial.