Proximity Features: privacy-aware cohort features for cold start¶

简体中文

Fidelity: core mechanism. Runs dense hash refinement, sparse fine-to-coarse clustering, stable proximity keys, cohort aggregation, and cold-start scoring.

Paper information¶

Field	Details
Paper	arXiv 2607.12246
Organization	Airbnb
First public release	2026-07-14 (arXiv v1)
Authors' code	The paper did not provide official or author code when checked on 2026-08-09.
Adapter / method	`proximity-features`
Local reproduction code	`src/auto_research/reproductions/proximity_features/`

Original paper¶

Motivation and method¶

Anonymous users have no user ID. Airbnb clusters consented geo-IP population-center coordinates into proximity keys of about 1,000 users. Dense locations split by IP hash; sparse locations progressively merge at coarser geographic precision. Cohort behavior is aggregated daily by stable key without persistent personal identifiers online.

flowchart LR
  A[Consented geo-IP] --> B[Hash refinement for dense locations]
  A --> C[Progressively merge sparse locations]
  B --> D[Stable proximity key]
  C --> D
  D --> E[Cohort feature aggregation]
  E --> F[Anonymous cold-start ranking]

Key figure from the paper¶

Figure 1: Core architecture, modules, and connections. From the original paper; copyright remains with the authors.

Core equations¶

\[ key=base64(\lfloor lat\,s\rfloor,\lfloor lng\,s\rfloor,h(ip)\bmod b), \]

\[ \max |\mathcal P|\quad\text{s.t.}\quad\sum_{i\in B_j}n_i\ge T,\ \forall B_j. \]

Paper results¶

Marketing pages report global bookings +0.011% and first-time bookers +2.0%. AutoSuggest reports global bookings +0.16% and first-time bookings +0.33%.

Local reproduction¶

Local comparison: The baseline is a global cold-start aggregate. The treatment uses adaptive MovieLens ZIP proximity aggregation with validation-selected blend 1.0. Relative Hit@10 is +16.67% and NDCG@10 +22.91%.

The 932 users with ZIP data form 99 buckets, median size 10. Cohort signal beats the global aggregate using all original item features. See the stable metrics.

auto-research reproduce --paper proximity-features --seed 42

Reproduction boundaries¶

ZIP prefixes are not geo-IP coordinates. The threshold is reduced to 12 for algorithm validation; this does not establish the paper's roughly 1,000-user privacy guarantee.