FastAPI makes it easy to stand up an AI endpoint quickly. The harder part is deciding what the contract should look like once the workflow includes retrieval, longer-running tasks, partial responses, and operational failure modes.
Many RAG systems disappoint for the same reason: the team treats retrieval as a single implementation choice instead of an evolving product capability. In practice, different query classes need different strengths.
The fastest way to create a fragile AI system is to treat every step as an open-ended model decision. The fastest way to create a usable one is to decide, explicitly, where determinism should live and where the model is actually adding value.