Yup! That's how most people run Headway right now. You can probably get by with around 2GB of RAM for a medium-sized metro, possibly even less.
Also for full-planet requirements, the OVH box running maps.earth has 64GB of RAM and 6 physical cores and is really struggling right now. Load average is about 40, most its CPU time is spent on the Valhalla service. Really enjoying watching the metrics right now :)
You may have chosen Valhalla for other reasons, but FWIW I’ve found Graphhopper can handle 1-2 orders of magnitude more qps than Valhalla on the same hardware.
I wasn't happy with cycling directions in GraphHopper and I was having trouble getting route shapes from its routing endpoint which made it really difficult to plot route polylines on the map. I've also been looking forward to exposing some customization of routing parameters since valhalla allows you to do this fairly trivially. That is good to know, though. Valhalla really is getting hammered by all this traffic. :/
What problems did you face with cycling directions?
Regarding the route shapes I can only guess: we use an encoded polyline as default for a very compact response. You can either disable this or use our JavaScript library, or there is a new UI https://github.com/graphhopper/graphhopper-maps
