4. Deezer overview
/01 Context
Story of the algorithms behind Deezer Flow
● Music streaming service
● 6M paying users
● 40M tracks
● 180+ countries
● Up to 200+ tracks / user
/ day
5. Story of the algorithms behind Deezer Flow
Adapt tracklist to
● Music tastes
● Localization
● Activity
● Mood
● Time & day
● Discovery preferences
Interesting debate
Should we ask questions to the user
or let data science do the magic?
Deezer Flow: Initial pitch
The magic play button
Context/01
7. /02 Initial system
Story of the algorithms behind Deezer Flow
Available data:
● User likes (artists, albums,
tracks)
● User streams logs
● Album recommendation
algorithm (collaborative
filtering)
Initial System (2014)
Strategy:
● Tracklist computed offline
● Tracks from library / listening
habits
● Tracks from recommended
albums
8. /02 Initial system
Story of the algorithms behind Deezer Flow
Cold start problem: addressing new users
1. New users are asked to select
some musical genres, and some
artists
2. Build tracklist based on liked artists
& similar artists
3. Fallback to top tracks in country
9. /02 Initial system
Story of the algorithms behind Deezer Flow
● Tracklist only fits user’s tastes
● Tracklist do not fit user’s mood or user’s
activity or time ...
To reach this goal:
● Immediately take into account user’s
last interactions
● Refresh tracklist more often
● Insights into the content of a track
Need a more content-based approach
First Flow limitations
11. /03 Content tagging system
Story of the algorithms behind Deezer Flow
Building a content tagging system
12. /03
Story of the algorithms behind Deezer Flow
● Heterogenous sources
● Millions of songs, artists, playlists
or albums to tag everyday
Quality assessment:
● Monitoring every sources
● Benchmarking
● Studying new metrics
How to consolidate such data?
Content tagging system
13. /03 Content tagging system
Story of the algorithms behind Deezer Flow
Architecture overview
Content data:
- Tags
- Popularity
User data:
- Taste model
- Hot tracks
- Behaviors
Build tracklist
- Data cache
- User action history
- Update user models
- Consolidate tags data
- Build indexes
actions logs
15. The live Flow (2015)
● Generated user profile
● User history analyzed offline
● Recently played tracks
● Recent actions
● Querying tracks from ElasticSearch index
/04 Live adaptive algorithms
Story of the algorithms behind Deezer Flow
16. Story of the algorithms behind Deezer Flow
Flat tag profiles can lead to mistakes
● Tag clustering
● Querying ES with different tag queries
● Serving tracks according to cluster
proportion
/04
We can be more precise!
Live adaptive algorithms
17. Different metrics to follow:
● Listening time
● Satisfaction
● User interaction (skipped / liked)
● Reconnection to Flow
Live evaluation - AB Testing
/04 Live adaptive algorithms
Story of the algorithms behind Deezer Flow
19. Story of the algorithms behind Deezer Flow
What‘s next ?
● Fitting to user’s mood
● Increased performance on first
days
Where are we now?
● Collaborative filtering combined
with Content-Based approach
(coming soon)
● More adaptation to the context
Conclusion/05
20. We are hiring!
Story of the algorithms behind Deezer Flow
● Data scientist
● Data architect
● Search scientist
https://www.deezer.com/jobs
Conclusion/05