I am basically looking for something faster than grep
You're unlikely find anything much faster than grep - it's a program a written in C and optimised to scan though a text file printing out lines that match. You may also be running into IO limits. For example, you could try
time wc -l bigfile
Which will effectively give you a lower bound (just read the the contents of the file, and find the \n's). If the grep isn't a whole lot slower than that, then there's probably no way to speed it up.