Interview: cluster 5M e-commerce customers for a marketing campaign.

hard

Answer

$(1) Define business goal (targeting, retention, cross-sell?).$
$(2) Sample 500k for prototyping.$
$(3) Build RFM + behavioral features + demographic.$
$(4) Log-transform skewed features + z-score.$
$(5) PCA/UMAP to 30 dim.$
$(6) Try mini-batch k-means (k=5-10) and HDBSCAN.$
$(7) Metrics: silhouette + business KPI (per-cluster conversion / LTV).$
$(8) Profile clusters: mean features + tree surrogate + medoid examples + name each.$
$(9) Stability check.$
$(10) Deploy to full 5M via saved pipeline; retrain quarterly.$

Check yourself — multiple choice

Random
Business goal + sample 500k + RFM/behavioral features + log-transform + z-score + UMAP + mini-batch k-means or HDBSCAN + silhouette + business KPI + profile + stability + deploy + quarterly retrain
Just k-means
Not real

5M seg: goal + sample + RFM + log/z-score + UMAP + mini-batch KM/HDBSCAN + KPI.

#interview#clustering#applications

214 interview questions in this topic.