This document summarizes a presentation about Pollfish, a mobile survey platform. It discusses how Pollfish collects data from over 170 million mobile devices worldwide through surveys and device/user information. It handles big data by storing raw data in HDFS and using Cassandra for time-series and user profile data while PostgreSQL stores aggregated data. Spark is used for general cluster computing. Machine learning models use survey data to classify users into personas to personalize surveys. The system architecture includes HDFS, Cassandra, PostgreSQL, Azkaban for workflows, and Spark.

1. Euangelos Linardos
Data Scientist @ Pollfish Inc
2nd Athens Data Science Meetup, Athens 17 December 2015
Data at Pollfish

2. Twitter: @eualin Email: euangelos@pollfish.com
I AM EUANGELOS LINARDOS

3. THE CONCEPT
PART I

4. ABOUT POLLFISH
Pollfish is a mobile survey platform that delivers online surveys globally.
Pollfish ensures your survey reaches just the right audience and provides the most cost
effective, quick and accurate survey results.

5. DIY SURVEY TOOL

6. PUBLISHERS NETWORK
MORE THAN 170M MOBILE DEVICES ALL OVER THE WORLD

7. UNIQUE USER EXPERIENCE

8. A WIN WIN WIN SITUATION
I WIN, YOU WIN
EVERYBODY WINS

9. REAL-TIME RESULTS

10. SUPERIOR QUALITY

11. IT DOESN’T MATTER WHAT WE SAY
CLAIM YOUR FREE COUPON
AND TRY IT NOW

12. NATURE OF DATA
PART II

13. MOBILE SURVEYS IS
A BIG DATA BUSINESS

14. VOLUME
● UNIQUE USERS:
~2 M daily
~15 M monthly
~170 M total
● DATA TRAFFIC:
~1 TB daily
~26 TB monthly
~210 TB total
* volume = scale of data

15. THAT’S A LOT OF SELFIES

16. VARIETY
● survey
● location
● device
● weather
● network
● publisher
● language
● and many more
* variety = different forms of data
PERSONA (200+)

17. ≠
VARIETY
"taxonomy" and "persona" are used
Interchangeably throughout this presentation!
[TAXONOMY = FEATURE ] [PERSONA = COMB. OF FEATURES]

18. VELOCITY
● ~11 M requests per day; on every request:
detect possible fraudulent activity
predict user action (start, finish, abort)
OF WHICH…
● ~13% accounts for classifications (new users)
1 update / user / taxonomy
● ~87% accounts for “traditional” lookups (old users)
1 lookup / user
* velocity = analysis of streaming data

19. VERACITY
● survey answers may be inaccurate
● device location data may be misleading
● 3rd party data may be outdated or wrong
* veracity = uncertainty of data

20. Too much to store on a single computer.
We need a cluster to process it.
This is typically what is called “Big Data”.
Amazing dataset to slice and dice!

22. DATA PROCESSES
PART III

23. MAIN DATA OPERATIONS
● Reporting
● Business Analytics
● Operational Analytics
● Product Features

24. REPORTING

25. REPORTING
● GROUPS OF INTEREST:
publishers
researchers
● EXAMPLE QUERIES:
# of surveys completed through my app?
# of users completed my survey?

26. BUSINESS ANALYTICS

27. BUSINESS ANALYTICS
● GROUPS OF INTEREST:
sales and operations
management, executives and investors
● EXAMPLE QUERIES:
count number of (daily, weekly etc.) active users
analyze growth, user behavior, sign-up funnels
company KPIs (Key Performance Indicator)
NPS analysis (Net Promoter Score)
* KPI: evaluate the success of an organization.
* NPS: measure the loyalty of a firm’s customer relationships.

28. OPERATIONAL ANALYTICS

29. OPERATIONAL ANALYTICS
● GROUPS OF INTEREST:
devops engineers
data engineers
● EXAMPLE QUERIES:
latency analysis: msec to wait for survey after loading the app
capacity planning: server, people, bandwidth etc.
root cause analysis: locates the root causes of faults

30. PRODUCT FEATURES

31. PRODUCT FEATURES
● Data enrichment
● Publisher classification
● Fraud detection
● User personas
● A/B testing

32. SURVEY PERSONALISATION IS THE FUTURE!

33. SURVEY
... should fit your mood.
... should fit your activity.
... should be personal!

34. IF YOU LOOK LIKE THIS #1
Gender: male
Age: 24-34
Marital status: single
Location: california
Interest: sports
salary: 150K
Show PERSONAL
survey! #1

35. SURVEY SHOULD FOLLOW #1
Gender: male
Age: 24-34
Marital status: single
Location: california
Interest: sports
salary: 150K
interested in
buying the
latest convertible
from
BMW?

36. IF YOU LOOK LIKE THIS #2
Gender: male
Age: 34-44
Marital status: married
Location: helsinki
Interest: video games
salary: 90K
Show PERSONAL
survey! #2

37. IF YOU LOOK LIKE THIS #2
Gender: male
Age: 34-44
Marital status: married
Location: helsinki
Interest: video games
salary: 90K
interested in
buying the
latest SUV from
VOLVO?

38. OVERCOME THE CHALLENGE
Challenge:
survey data is accurate but limited. How do you scale?
Solution:
dedicated machine learning models using quality survey data.
Pollfish Personas:
targetable groups of consumers with similar characteristics, based on device, location data,
and most importantly, survey answers!

41. POLLFISH PREDICTORS
Multivariate:
persona probability score calculated based on all available attributes.
Daily Updated:
keep your models current with daily model refreshments.
With Customizable Threshold:
customize threshold for precision or recall.

42. SYSTEM ARCHITECTURE
PART IV

43. TO MAKE DATA-DRIVEN DECISIONS
DATA AND INFRASTRUCTURE
ARE REQUIRED (AMONG THE OTHERS).

44. HIGH LEVEL ARCHITECTURE

46. HDFS
● more data usually beats better algorithms
● raw data is:
complicated
often dirty
evolving structure
duplication all over
● getting data to a central point is hard! #NOT
● it's simple! we just throw them into HDFS!

47. C*
● a distributed and linearly scalable and distributed key-value store
● ideal for time-series data
● provides fast random access for many small pieces of data
● use it for surveys, user profiles, popularity count and almost anything

48. POSTGRESQL
● we still use it, a lot!
● powering features that require transactions support, integrity constraints, and more
● aggregated data for dashboard and quick analysis

49. CRITICAL AND CONSISTENCY
IMPORTANT? → POSTGRESQL
HUGE, GROWING FAST, EVENTUAL
CONSISTENCY OK? → CASSANDRA
RAW AND HISTORICAL? → HDFS

50. AZKABAN
● allows us to build pipelines of batch jobs
● handles dependency resolution, workflow management, visualisation and more
● the alternative to Luigi and Oozie

51. SPARK
● general cluster computing platform:
distributed in-memory computational framework
SQL, Machine Learning, Stream Processing, etc.
● easy to use, powerful, high-level API:
Scala, Java, Python and R

52. TIPS FOR DEVELOPING DATA PRODUCTS
● Collect data, data, DATA!!!
● Large amounts of data can reveal new patterns
● Be careful of “black box” approaches
● Look at your raw data (exploratory analysis)
● Aggregate statistics can be misleading
● Visualize your data
● Include data geeks in design process
● Find opportunity in your error data

53. Thank you
(we’re hiring):
https://pollfish.workable.com/