We have been working on that for the past few month. Right now the performance is pretty good for C++ projects up to around 2 million lines of code. For C projects the performance is even better! If you want to test it, just download the pre-indexed clang project (900k loc) from our website (https://www.sourcetrail.com/downloads#extra). Indexing the project took 12 minutes on a 5 year old laptop.