We consider the design and implementation of a centralised oracle that provides commuters with customised and congestion-aware driving directions. Computing directions for a single journey is straightforward, but doing so at city-scale, in real-time, and under changing conditions is extremely challenging. In this work we describe a new type of centralised oracle which combines fast database-driven path planning with a query management system that distributes work across a small commodity cluster of networked machines. Our system allows large-scale changes to the underlying graph metric, from one query to the next, and it supports a variety of query types including optimal, bounded suboptimal, time-budgeted and k-prefix. Simulated experiments show strong results: we can provide real-time routing for all peak-hour commuter trips in the city of Melbourne, Australia.