33M vertices and 1B edges easily fits into memory, if you use 32 bit integers, it will require about 4 GiB of memory. Out of curiosity I just implemented generating a random graph of that size and calculating one page rank iteration on it in the most naive way (20 lines of C#) and it consumed 8.4 GiB of memory and got one iteration done in 4:20 minutes single threaded.

> most existing graph algorithms require the graph to fit into memory.

You can get pretty far with sparse graphs, which are just arrays, in combination with memory mapping.