Cosmo Router is a high-performance GraphQL API Gateway / Router compatible with Apollo Federation v1 and v2, designed to be an open-source drop-in replacement for Apollo Gateway and Apollo Router. It features a new Dataloader implementation that provides a 3.3x performance improvement over the previous implementation, making it more efficient and resource-friendly. Additionally, Cosmo Router introduces Ludicrous Mode, which allows it to send origin requests that are read-only using single-flight, reducing the load on the origin. The router also supports Open Federation and is compatible with Apollo Federation v1 and v2 as well as Open Federation. It includes Open Telemetry (OTEL) instrumentation for monitoring API traffic, allowing users to identify bottlenecks and optimize their system.