For the moment: you can have as much data as you want on disk as long as the RocksDB storage engine can handle it, which I believe is quite large. For any single query though, you want all the data you touch to fit in memory. The good news is that Rust is very efficient in using memory. This will be improved in future versions.

For the built-in graph algorithms, you are also limited by the algorithmic complexity, which for some of them is quite high (notably betweenness centrality). There is nothing the database can help in this case, though we may add some approximate algorithms with lower complexities later.