Weights & Biases documented their journey refactoring Wandbot, their LLM-powered documentation assistant, achieving significant improvements in both accuracy (72% to 81%) and latency (84% reduction). The team initially attempted a "refactor-first, evaluate-later" approach but discovered the necessity of systematic evaluation throughout the process. Through methodical testing and iterative improvements, they replaced multiple components including switching from FAISS to ChromaDB for vector storage, transitioning to LangChain Expression Language (LCEL) for better async operations, and optimizing their RAG pipeline. Their experience highlighted the importance of continuous evaluation in LLM system development, with the team conducting over 50 unique evaluations costing approximately $2,500 to debug and optimize their refactored system.
