Escaping SDK maintenance hell with a core Rust engine

Statsig, a company managing over 24 SDKs with a small development team, has transitioned to a centralized Rust-based core engine to improve efficiency and performance across its server-side features. Previously, each SDK required duplicating evaluation logic across multiple languages, creating significant maintenance challenges. By consolidating the most popular server SDKs—Node, Python, Elixir, Java, and Rust—into a single Rust core, the company has achieved up to fivefold improvements in evaluation speeds, alongside enhanced code sustainability. Despite initial challenges and increased workload during the transition, the move aims to decouple developer resources from the number of supported languages, allowing for faster feature deployment and long-term maintenance simplification. The project utilized various Foreign Function Interfaces (FFIs) to create bindings for different languages, and the team acknowledges the supportive Rust community for aiding in the learning and implementation process. Moving forward, Statsig plans to focus new developments on the Server Core SDKs, maintaining legacy SDKs in a limited capacity, and anticipates that this strategic shift will streamline future updates and development efforts.