Airbnb just rewired Mussel, its key-value store, with a smarter, layered QoS system. Out go the rigid QPS caps. In come resource-aware rate control, criticality-based load shedding, and real-time hot-key mitigation.
Dispatchers now speak the language of backend cost -rows, bytes, latency - not just raw request counts. Quotas are enforced in actual resource units. Local defenses like CoDel queues and Space-Saving counters add muscle, soaking up spikes and shrugging off DDoS bursts without flinching.
