Case Study · Search & Discovery

Lifting search CTR ~22% by ranking on real behavior, not metadata.

Search is Joyn's second-largest acquisition source, with 60-70% of searchers converting onward — but Algolia ranked on static catalog text alone, and dead-end queries had no recovery. Rebuilt in two phases into a behavior-driven, self-improving ranking and fallback system, with zero added latency at millions-of-DAU scale.

Role Architected and led the search relevance rebuild — signal pipeline, GDPR governance, and hybrid reranking

2021-current Joyn · ProSiebenSat.1 streaming #2 acquisition source on home 60–70% search-to-detail conversion Millions of DAU served

Search is the second-biggest door into the catalog

High traffic through search wasn't translating into proportional relevance — vendor ranking couldn't see what users actually did next.

DISCOVERY

Search drives conversion at scale

Search is Joyn's second-largest home page acquisition source, behind only the hero lane. Most sessions that reach it convert onward.

60–70% = search → content
RELEVANCE

Algolia ranked on metadata alone

Results were ordered by static catalog text, with zero visibility into clicks, views, or watch-time. Relevance couldn't improve itself.

No behavioral signal reaches Algolia = ranking can't learn from real usage
DEAD ENDS

Zero-result queries had no recovery

A near-miss query returned nothing and no alternative path, pushing users straight to bounce.

Zero results, no fallback = users bounce

What kept ranking stuck on metadata

Three constraints — data access, compliance, and architecture — had to be solved together before relevance could improve.

DATA

No first-party feedback loop

Click-throughs, video views, and watch-time lived in Joyn's systems but never reached Algolia's ranking model.

Click/view/watch data trapped internally = ranking never learns
COMPLIANCE

GDPR governed every signal

Any pipeline sending user behavior to a third-party search vendor required consent handling and Legal sign-off.

Every signal needs Legal sign-off = compliance blocks the pipeline
ARCHITECTURE

Single-vendor, single-signal ranking

Algolia's core results had no layer to blend keyword relevance with Joyn's own recommendation models.

No blending layer = keyword relevance is the ceiling

Two phases: feed signals in, then rerank and recover

First-party behavioral data closed the feedback loop with Algolia; a custom layer then handled fallbacks and reranking on top.

1
First-party signal pipeline consented users → Algolia

Built a pipeline transmitting click-throughs, video views, and watch-time from consented users directly to the search index.Algolia · event pipeline

2
GDPR-compliant governance

Partnered with Data Science and Legal to validate consent scope and data sharing before any signal went live.Legal · Data Science

3
Behavioral feedback loop

Embedded the new signals into Algolia's ranking model, shifting it from static metadata matching to behavior-driven relevance.Algolia · ranking model

4
Hybrid reranking + zero-result recovery

Built a custom reranking layer on Algolia's results using in-house ML, and shipped personalized fallbacks for zero-result queries.In-house recsys · reranking

Behavior-driven ranking, at full scale

+17%
CTR — Phase 1
Signal integration
+4.7%
CTR — Phase 2
Reranking & fallbacks
~22%
Net CTR increase
Combined phases
-30%
Zero-result queries
Friction reduction

From single-vendor ranking to a compounding relevance engine

⚡

A virtuous data cycle, at zero latency cost

First-party behavioral data now feeds ranking continuously, scaling to millions of daily active users with zero latency degradation — relevance improves itself with every session.

✕

Dead ends eliminated

Zero-result recovery preserves user intent instead of ending the session at an impasse.

⊕

Hybrid search architecture

Keyword relevance and ML-driven engagement signals now combine, outperforming either alone.

↻

Reusable recommendation layer

The in-house reranking model built for search now generalizes to other discovery surfaces.

⟲

Cross-functional velocity as default

Early Product, Data Science, Engineering, and Legal alignment became the template for shipping compliant data features fast.

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