1. A graph storage and processing system, comprising: a scalable, distributed, fault-tolerant, in-memory graph storage device for storing base graph data representative of graphs; a real-time, in memory graph storage device for storing update graph data representative of graph updates for the graphs with respect to a time threshold; an in-memory graph sampler for sampling the base graph data to generate sampled portions of the graphs and for storing the sampled portions of the graph; a query manager for providing a query interface between applications and the system and for forming graph data representative of a complete graph from at least the base graph data in the scalable, distributed, fault-tolerant, in-memory graph storage device and the update graph data, if any, in the real-time, in memory graph storage device; and a graph computer for processing the sampled portions of the graphs using batch-type computations to generate approximate results for graph-based queries.