Cosmos DB case study shows hot partition fix cut RU use from 100% to 20–35%

At Azure Cosmos DB Conf 2026, a production case study showed how a system stuck at 100% RU utilization and rising P99 latency was traced to a single logical partition taking over 80% of traffic. After correcting the data model, RU usage fell to about 20–35%, throttling disappeared, and latency normalized without adding throughput.