The domain name availability has seen a critical point in the last decade and that is the reason why so many extensions are being created to get rid of this problem. There is virtually no way to find any .com extension that is shorter than 5 letter without paying premium. Even combinations of letters that don’t create real words is impossible to find.
If you want to have a good domain name, you need to find one that is short, but also one that is going to be very easy for people to remember when they hear it or read it from any kind of advertisement and media. With that said, your quality and consistency of content will be the most relevant even if your domain name is not optimal.