We use Protocol Buffers for our schemas (and schema evolution rules) to keep all layers of the distributed system in sync, including mobile apps, web service, and data warehouse.
The Stack That Helped Medium Drive 2.6 Millennia of Reading Time
Dan Pupius

Do you also use PB schemas for XHR? I see JSON over the network; do you convert PB to JSON, or have some other special schemas for front-ends?