My talk at NDF Conf 2021

1. Machine Learning in
Online Marketplaces
Alexey Grigorev
04.05.2021

2. Today you’ll learn:
Practical use cases of ML
in two-sided marketplaces

3. Hello 👋
I’m Alexey.

4. Plan
● Marketplace
● Examples of marketplaces
● Use cases of ML in marketplaces
○ Search
○ Recommendation
○ Trust and Safety
○ Seller experience
○ Pricing and monetization
○ Other examples
● Conclusion

5. Source: https://www.dvnovosti.ru/eao/2019/08/24/103683/

6. Seller

7. Seller
Icons: Bananas, Apple

8. Buyer Seller
Icons: Bananas, Apple

9. Buyer Seller
Icons: Bananas, Apple
💶
💶
💶

10. Buyer Seller
Icons: Bananas, Apple
💶
💶 💶

11. Buyer Seller
Icons: Bananas, Apple
Marketplace

12. Buyer Seller
Online
Marketplace
Icons: Bananas, Apple
Website
💳

19. Buyer
(Demand side)
Seller
(Supply side)
Online
Marketplace
Website

20. ML in online marketplaces
● Recommendations
● Search
● Trust and safety
● Seller experience
● Pricing and monetization
● Other examples

22. Icons: srip

23. Amazing 5G phone
With 100500 GB RAM
10 cameras
Unlimited disk space
Customers who bought this also bought ...
Icons: srip

24. Algorithms
● Counting
● Collaborative filtering
● Neural networks

25. Icons: srip

26. Counting
SELECT country, item, count(1)
FROM views
GROUP BY country, item

27. Collaborative filtering
A
Users
Items
≈ U V
x

28. Collaborative filtering
Users
Items
≈ x
Item
vector
User
vector

29. d2
d1
󰬋
🧦
🧸

30. d2
d1
󰬋
🧦
🧸

31. Amazing 5G phone
With 100500 GB RAM
10 cameras
Unlimited disk space
Customers who bought this also bought ...
Icons: srip

32. Collaborative filtering
Icons: srip
similarity

33. Neural networks (“item2vec”)
Icons: srip
Neural network
Neural network
similarity

34. https://habr.com/ru/company/avito/blog/491942/
Deep Learning Recommender Systems - Cristian Martinez, Ilia Ivanov (video)

35. ML in online marketplaces
● Recommendations
● Search
● Trust and safety
● Seller experience
● Pricing and monetization
● Other examples

36. Cool devices
Icons: srip
🔍

37. Algorithms
● Bag of words and TF-IDF
● Learning to rank

38. Amazing 5G phone
With 100500 GB RAM
10 cameras
Unlimited disk space
Icons: srip
Apache
Lucene
Index

39. Amazing 5G phone
With 100500 GB RAM
10 cameras
Unlimited disk space
Icons: srip
Apache
Lucene
Cool devices
Index
Query

40. TF-IDF
Q: {"cool": 1.1, "device": 1.2}
D1: {"apple": 1.2, "5g": 1.0, "hip": 1.5}
D2: {"samsung": 1.1, "joystick": 1.7, ...}
D3: {"hp": 2.2, "laptop": 1.2, "used": 0.6, ...}
D4: {"deep": 0.9, "learning": 1.0, "printer": 2.3, ...}

41. doc
query
θ
angle between vectors
w2
w1

42. Learning to rank
Query 1 Document 1 Yes
Query 1 Document 2 No
Query 1 Document 3 No
Query 2 Document 1 No
Query 2 Document 2 No
Query 2 Document 3 Yes

43. Query (user)
Document
Model P(relevant)

44. Query
Document
Neural network
Neural network
similarity

45. ML in online marketplaces
● Recommendations
● Search
● Trust and safety
● Seller experience
● Pricing and monetization
● Other examples

46. User generated content
Such description. So much text

47. User generated content
Such description. So
much text
Such description. So
much text
Such description. So
much text

48. User generated content

49. Problems:
● Illegal content
● NSFW content
● Duplicates
● Spam
● Fraud

50. Content moderation
Such description
So much text

51. Content moderation
ML
Such description
So much text
Automatic
moderation system

52. Content moderation
ML
Such description
So much text
Accept
Reject
Moderation queue
MP
Automatic
moderation system
Moderation panel
Accept
Reject
Moderators

53. ML
Automatic
moderation system
Duplicates
Forbidden
items
NSFW
Spam Fraud

54. category:
Truck
category:
Fridge
category:
Machete
Forbidden items

55. https://tech.olx.com/a-two-step-framework-for-duplicate-detection-fbbe4c905480
https://tech.olx.com/detecting-image-duplicates-at-olx-scale-7f59e4b6aef4

56. ML in online marketplaces
● Recommendations
● Search
● Trust and safety
● Seller experience
● Pricing and monetization
● Other examples

57. I want to
sell my
car
Picture by John Torcasio from unsplash (source)

58. Picture by John Torcasio from unsplash (source)
��

59. ��

60. ��

61. 🚗 Model Price

62. ��
🥳
50000

63. quality:
Good
quality:
Bad
Image quality

64. AI in online marketplaces
● Recommendations
● Search
● Trust and safety
● Seller experience
● Pricing and monetization
● Other examples

65. ��

66. ��
🚗

67. ��
🚗
Icons: Concert

68. ��
🚗
Icons: Concert
��
��
��
�� ��
🚗
🚗
“Surge”

69. Icons: srip
Cool devices
🚀
Awesome
Promoted
Ad
🔍

70. ML in online marketplaces
● Recommendations
● Search
● Trust and safety
● Seller experience
● Pricing and monetization
● Other examples

71. Other examples
● Customer support
● HR
● Finance

72. Plan
● Marketplace
● Examples of marketplaces
● Use cases of ML in marketplace
○ Search
○ Recommendation
○ Trust and Safety
○ Seller experience
○ Pricing and monetization
○ Other examples
● Conclusion

73. Conclusions
● ML in marketplaces is everywhere
● ML helps buyers: search, recommendation, trust and safety
● ML helps sellers: seller experience
● ML helps make money: pricing and monetization
● ML helps the organization: HR, customer support

76. @Al_Grigor
agrigorev
DataTalks.Club