Skill mapping is a key task in the Human Resources domain. It consists in identifying ontology-defined skills in job texts. Among the most successful approaches applied to skill mapping, bi-encoders offer efficient inference but struggle with fine-grained skill distinctions, particularly under limited supervision. While accurate, cross-encoder and LLM-based reranking approaches are computationally expensive and usually not feasible to be adopted in real case scenarios. We propose kNNBE, a hybrid inference method that augments bi-encoder similarity scores with k-nearest labeled sentences drawn from a synthetic memory bank. kNNBE improves both prediction accuracy and generalization to unseen skills while retaining high throughput. Extensive experiments on three benchmark datasets show that kNNBE rivals state-of-the-art rerankers in accuracy while being orders of magnitude faster.
