"Buy It Now! Cassandra at eBay" talk at Cassandra Summit 2013 This session will cover various use cases for Cassandra at eBay. It’ll start with overview of eBay’s heterogeneous data platform comprised of SQL & NoSQL databases, and where Cassandra fits into that. For each use case, Jay will go into detail of system design, data model & multi-datacenter deployment. To conclude, Jay will summarize the best practices that guide Cassandra utilization at eBay. http://www.datastax.com/company/news-and-events/events/cassandrasummit2013

1. Cassandra @ eBay
Jay Patel
Architect, Platform Systems
@pateljay3001

2. eBay Marketplaces
Thousands of servers
Petabytes of data
Billions of SQLs/day24x7x365
99.98+% Availability
turning over a TBevery second
Multiple Datacenters
Near-Real-time
Always online
400+ million items for sale
$75 billion+ per year in goods are sold on eBay
Big Data
112 million active users
Billions of page views/day

3. 3
eBay Site Data Infrastructure
Don’t force!
One size does not fit all.
It’s a mixture of
multiple SQL &
NoSQL databases.
We use the right
database for the
right problem.

4. eBay Site Data Infrastructure
A heterogeneous mixture
Thousands of nodes
> 2K sharded logical host
> 16K tables
> 27K indexes
> 140 billion SQLs/day
> 5 PB provisioned
Hundreds of nodes
Persistent & in-memory
> 40 billion SQLs/day
10+ clusters, 100+ nodes
> 250 TB provisioned
(local HDD + shared SSD)
> 9 billion writes/day
> 5 billion reads/day
Hundreds of nodes
> 50 TB
> 2 billion ops/day
Thousands of nodes
The world largest
cluster with 2K+ nodes
Dozens of nodes

5. How do we scale RDBMS?
 Shard
– Patterns: Modulus, lookup-based, range, etc.
– Application sees only logical shard/database
 Replicate
– Disaster recovery, read availability & read scalability
 Big NOs
– No transactions
– No joins
– No referential integrity constraints 5

6. Why Cassandra?
 Multi-datacenter (active-active)
 Always Available - No SPOF
 Easy to scale up & down
6
 Write performance
 Distributed counters
 Hadoop support
Not replacing RDBMS, but complementing!
 Some use cases don’t fit well in RDBMS - sparse data, big data,
flexible schema, real-time analytics, …
 Many use cases don’t need top-tier set-ups.

7. Cassandra Growth
Aug,2011
Aug,2012
ay,2013
1
2
3
4
5
6
7
Billions
(per day)
writes
async. reads
sync. site reads
Terabytes
50
100
200
250
300
350
storage capacity
Doesn’t predict
business
7

8. eBay Use Cases on Cassandra
 Time-series data, real-time insights & immediate actions
• Fraud detection & prevention
• Quality Click Pricing for affiliates
• Order & shipment tracking and insights
• Mobile notification logging & tracking
• Cloud CMS change history storage
• RedLaser server logs and analytics
 Server metrics collection for monitoring & alerting
 Taste graph based next-gen recommendation system
 Personalization Data Service
 Social Signals on eBay Product & Item pages
 Milo’s store-item availability inventory (evaluation phase) 8

9. Real-time insights & actions for
9
Fraud Prevention Reporting
Quality Click Pricing More…

10. 10
System Overview
Business Event Stream
Checkout Shipping Refund & Recoup …
Order placed
(bin/bid)
Paid Shipped Refunded
Rawdata
Simple in-memory aggregations +/
Complex Event Processing +/
Cassandra’s distributed counters
Label printed per day per user
User segmentation for affiliate pricing
Orders per hour, …
Multiple Cassandra clusters
Payment
Actinreal-time
Fraud Prevention
Affiliate Pricing Engine
(eBay Partner Network)
Order tracking
Real-time reporting
…
(Kept from several months to years)

11. A glimpse on Data Model
11
Historic & real-time insights per user per carrier.
Sudden & drastic change might be suspicious.
User bucketing based on historic
& real-time buying activity.

12. A glimpse on Data Model
12

13. Fraud Detection & Prevention
13
Shop with Confidence

14. System Overview
14
Cassandra
Fraud Detection & Prevention System
Sign-ininfo
Business events
(checkout, sell,…)
StaaSOracle
Checkout Shipping …PaymentSelling
Real-time
Beacons data
Real-time
Insights
Other data
Machine
Learned Models

15. 15
A glimpse on Data Model
Collected at sign-in
& stored as key-value.
Pulled periodically to StaaS for
training machine learned models.

16. Metrics collection for monitoring & alerting
16

17. System Overview
17
Transport (HTTP, …)
Scalable NIO
servers based
on Netty
Thousands of
production
machines
Cassandra
Stats for CPU, Memory, Disk, ..
…
agent agent agent agent …
Server Server Server Server Server
In-memory grid (hazelcast) for rollups

18. A glimpse on Data Model
18
Granular data points
Rolled up metrics
for various time intervals

19. Taste graph based recommendation system
19

20. Data Model
20
TasteGraph
TasteVector
50 billion+ edges, 600 million+ writes, 3 billion+ reads, 30TB+ of data on SSD

21. System Overview
21
Business Event Stream
Recommendation system
Taste GraphTaste Vector
1. Item purchased.
2a. Write purchase edge.
2b. Read other edges for this user & item.
4. Req. recommendations.
5. Finds other items close to
user’s coordinates.
6. Reco. shown to user
More, http://www.slideshare.net/planetcassandra/e-bay-nyc

22. Real-time Personalization Data Service
22
User performs search using keyword User gets personalized pages based on
implicit/explicit profile

23. System Overview
23
Personalization Data Service
CacheMesh
(write-back cache)
Heavy writes
eBay site pages (personalized)
Every few mins
in-memory
MySQL
& XMP DB
CassandraOracle
(scaled out) Heavyreads
Cache miss
user profiles
Application SOA services (multiple)
Data
Warehouse

24. Data Model
24
• Keep column names short.
• Don’t overload one CF with all the data:
- Split hot & cold data in separate CF.
- Splitting & sharding can help compaction.
Static column families

25. 25
Served by
Cassandra
Social Signals

26. Manage signals via “Your Favorites”
26
Whole page is
served by
Cassandra
More, http://www.slideshare.net/jaykumarpatel/cassandra-at-ebay-13920376

27. Multi-Datacenter Deployment
27
Topology - NTS
RF - 1:1 or 2:2 or 3:3
Read CL - ONE/QUORUM
Write CL - ONE
Data is backed up periodically
to protect against human or
software error
User request has no datacenter affinity
Non-sticky load balancing

28. Multi-Datacenter Deployment
Topology - NTS
RF – 1:1:1 or
2:2:2

29. Lessons & Best Practices
• One size does not fit all
– Use Cassandra for the right use cases.
• Choose proper Replication Factor and Consistency Level
– They alter latency, availability, durability, consistency and cost.
– Cassandra supports tunable consistency, but remember strong consistency is not free.
• Many ways to model data in Cassandra
– The best way depends on your use case and query patterns.
• De-normalize and duplicate for read performance
– But don’t de-normalize if you don’t need to.
http://www.slideshare.net/jaykumarpatel/cassandra-data-modeling-best-practices
29

30. Are you excited? Come Join Us!
30
Thank You
@pateljay3001
#cassandra13