Given Uber's service footprint, any solution for graceful degradation also has to be automatic and require no configuration because even if we require just a single configuration value per service, it will quickly be expensive in engineering hours, given the vast number of services we operate and how often such values tend to be outdated.
Uber used a scheme inspired by WeChat's approach, where priority value consists of the tier component (0 being the highest and 5 the lowest) and the cohort component, segmenting the user population.
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