Developed a user-specific rate limiting feature for the rails/rails repository, focusing on enhancing fairness and protecting critical endpoints from abuse. The solution scoped quotas per user by deriving a cache key from the target object, applying rate limits only when the object responded to cache_key, and included a guard to maintain backward compatibility for objects lacking this method. This approach aligned with existing Rails caching patterns to sustain performance and minimize request latency. The work was implemented using Ruby and Ruby on Rails, emphasizing backend and API development while prioritizing code quality, operational reliability, and seamless integration with established infrastructure.