Case Study: Microsoft Corporation achieves hyperscale reliability and elastic scaling for Cortana with Microsoft Azure Service Fabric

Building Bing Cortana as an always-on, hyperscale cloud service

Microsoft’s Cortana development team needed to build a reliable, highly available digital assistant that could scale from thousands to millions of users while delivering low-latency notifications (weather, traffic, news) across phones, tablets, and PCs. The primary challenges were achieving elastic scalability, geo-redundant failover, and stateful low-latency processing without spending months building complex infrastructure features from scratch.

The team implemented Reactor on Microsoft Azure Service Fabric—a microservices PaaS spanning three regions (120 VMs) with 1,200 query-engine instances and replicated stateful services. The result: automatic cross-datacenter failover with no user impact, support for 500 million evaluations per second, easy doubling of cluster capacity without architectural changes, portability between environments, and roughly three months faster time to market.

Microsoft Corporation

Ivana Markovic

Program Manager, Reactor Team