search

Binary search is simple to explain and notoriously easy to botch (off-by-one, infinite loops). Interviewers look for a correct template plus the variants (boundaries, rotated arrays) that show up constantly. The answer follows.

E-commerce search is where retrieval, ranking, and business goals meet, and it carries a strict exact-match requirement (brand, size, SKU). The signal is query understanding plus hybrid retrieval plus business-aware ranking. Here is the design.

Query understanding is the front end of search that converts a raw query into structured intent. Get it wrong and even a perfect index returns garbage. The signal is the pipeline and how you measure it. Here is the design.

A search box is a recommender carrying a strong prior: the query. The difficult pieces are reading ambiguous intent, retrieving in two stages within a tight latency budget, and learning from clicks without teaching the model that whatever appeared first is best.