RAG or fine-tuning: separate knowledge from behavior
CodeAstra Tech · Engineering decision guide
Start with the problem
Retrieval is useful when answers need access to documents that change or differ by user. It brings selected context into the request instead of treating the model as the source of truth.
Define the scope
Fine-tuning addresses learned behavior or patterns using examples. It does not replace an access-control layer or guarantee that changing business facts stay current.
Check the failure cases
Start by evaluating retrieval quality: whether the right source passages are found and whether the answer is supported by them. A model change cannot fix missing or wrongly permissioned source content.
Make the decision
Choose using representative evaluation cases. Some systems need retrieval alone, others combine approaches; do not add training complexity without evidence of the gap it solves.