Bi-encoders are probably the most efficient way of setting up a semantic Question Answering system. This architecture relies on the same neural model that creates vector embeddings for both questions and answers. The assumption is, both question and answer should have representations close to each other in the latent space. It should be like that because they should both describe the same semantic concept. That doesn’t apply to answers like “Yes” or “No” though, but standard FAQ-like problems are a bit easier as there is typically an overlap between both texts. Not necessarily in terms of wording, but in their semantics.

Read more in the article by Kacper Łukawski.