The document discusses moving an ad tech company's APIs from a monolithic application to microservices. It outlines the goals of helping advertisers spend money and publishers ensure ad quality. It also describes a pain point of delays in creative approval that took 36 hours in the old workflow. The proposed solution is to use an API to allow buyers to pre-submit creatives to eliminate delays. The document then provides best practices for splitting a monolith into microservices incrementally, building for failure, monitoring everything, and thoroughly testing changes.