July 2024 Summaries

The Cosmo Router is a GraphQL API Gateway that routes requests from clients to Subgraphs, implementing the GraphQL Federation contract. The Router can be built from source or run as a Docker container. Most users prefer using published Docker images for customizations. The Cosmo Router's goal is to minimize network requests. The article discusses three approaches to implementing the `@skip` and `@include` directives in the Router: Subgraph Directive Evaluation Approach, Smart but expensive Approach, and Zero-Cost Abstraction. The Zero-Cost Abstraction normalizes the query by removing unnecessary fields that are skipped or included using these directives, resulting in a significant reduction in latency and improved performance.

Graph Feature Flags are a powerful tool to enable isolated experiments and gradual rollouts of new features in GraphQL Federation. With Cosmo's Graph Feature Flags, you can experiment with new features in isolation and gradually roll them out to a subset of traffic in production. This is achieved through the creation of isolated compositions of Subgraphs where one or more Subgraphs are replaced with different versions, potentially incompatible with other isolated compositions. The approach allows for safe and controlled evolution of the Schema, reducing the need for centralized coordination across teams. Graph Feature Flags also enable gradual rollouts of new features to a subset of traffic in production, allowing for monitoring of performance and user experience impact. Additionally, they provide a declarative way to define Feature Flags, enabling build-time composition and preventing runtime errors due to incompatible Subgraphs. The solution is designed to be scalable, flexible, and efficient, making it an attractive option for organizations looking to improve their GraphQL Federation setup.

Cosmo Router generates smaller Subgraph Queries compared to Apollo Router, resulting in a performance improvement of up to 25% without changing a single line of code in the Subgraph. The Cosmo Router's approach to Query Planning involves AST Minification, which reduces the size of the Query by extracting common Selection Sets into Fragments and removing unnecessary fields and directives. The algorithm is stable and deterministic, making it easy to test and verify its correctness. By applying this optimization, users can reduce their spend on Subgraph Infrastructure and achieve faster Response Times, leading to better User Experiences, higher Conversion Rates, and ultimately more Revenue.