&gt; It seems like it would be much simpler and faster if they just took a default route from each provider and then did route probing on their top 30% prefixes in each PoP.<p>Probing just 30% of the top prefixes is likely not enough for their use case. Probing is also an after the fact approach. Fastly needs a solution which will give best possible path from first packet.<p>&gt; FWIW, the Netflix networks just take a default route from a pair of transit networks in each PoP. At their scale, they found it better to negotiate better worldwide transit deals than optimize networking at the PoP level. Different game than Fastly, but another data point.<p>Different game indeed. Netflix just cares about throughput, Fastly also needs low latency, hence the need for more optimizing.