eBay Inc. confidential

TRANSFORMING A RUNNING

LEGACY APPLICATION INTO HIGH

SCALABLE ARCHITECTURE

Morten Jokumsen

eBay classifieds

• Morten Jokumsen

• Software Architech

• Email: mjokumsen@ebay.com

• Skype: guidmaster

• Twitter: guidmaster

eBay Inc. confidential

Who and what is DBA?

• Old classifieds news paper started in 1981

• First website launched in 1995

• Sold to eBay in 2008

– Price: 370 mill UDS

3

eBay Inc. confidential

DBA 1996

4

eBay Inc. confidential

DBA 1997

5

eBay Inc. confidential

DBA 1999

6

eBay Inc. confidential

DBA 2000

7

eBay Inc. confidential

DBA 2002

8

eBay Inc. confidential

DBA 2004

9

eBay Inc. confidential

DBA 2005

10

eBay Inc. confidential

DBA 2007

11

eBay Inc. confidential

DBA 2008

12

eBay Inc. confidential

DBA 2010

13

eBay Inc. confidential

DBA 2012

14

eBay Inc. confidential

Who is DBA

• One of the largest websites in DK

• Grows 20% each year

• Mobile traffic goes crazy!

15

eBay Inc. confidential

THE CHALLENGE

16

eBay Inc. confidential

Get rid of this!

17

eBay Inc. confidential

Project Mercury

18

eBay Inc. confidential

Why Mercury?

19

Within the realm of astrology the planet Mercury is the ruler of the star sign Gemini. Gemini means twins.

This is what we want to do here seen from a business perspective: create a twin of dba.dk running on a more efficient, productive and high-quality platform.

eBay Inc. confidential

What we wanted

20

eBay Inc. confidential

Initial guidelines

• The architecture must be simple and uniform

• Use the Domain Driven Design patterns to gain uniform code and design of the

architecture

• Code should be high quality which means low bug count and high maintainability

• Performance need to be part of the architecture from the start

• The architecture is scalable, which made it's easy to scale horizontal by append more

servers to make higher throughput

• To ensure high quality and clean code, we migrate the existing database in steps to a

new database

• We migrate with a business scope one to one

21

eBay Inc. confidential

The challenges

• Move the architecture from 1999

• Totally new team

– Understand the business

• Move existing developers to .NET

• Totally new technology stack

22

eBay Inc. confidential

And how we did it the first time

23

eBay Inc. confidential

Why did it suck?

24

eBay Inc. confidential

AND WE DID THE SAME

MISTAKE IN THE NEXT PHASE

25

eBay Inc. confidential

The first write side

• Fighting the O/RM

• Anemic Domain Model

– Where did the logic go?

• Did we do it wrong?

– Layered architecture failed?

26

eBay Inc. confidential

LET´S SCALE

Evolve the code base

27

eBay Inc. confidential

The problems

• We could not scale

• We could not implement new stuff fast enough

• New developers had a hard time to understand the code base

• We said we we did DDD – but we didn´t

28

eBay Inc. confidential

CQRS TO THE RESCUE

29

eBay Inc. confidential

Our implementation of CQRS

30

eBay Inc. confidential 31

eBay Inc. confidential 32

eBay Inc. confidential

The advantage of CQRS

• We can scale

• We can implement new stuff fast!

• We have a clean code base

• New developers can easily follow the code base

• We know where logic should go

33

eBay Inc. confidential

The advantage of ES

• We can change the implementation of the domain

• We can scale

• Replay the stream

• We can debug and fix live bugs

• We have better business insight

34

eBay Inc. confidential

The new platform

35

ASP.NET MVC

MS SQL Server

jQuery

DDD

FAST

Nagios

Memcached

LINQ2SQL

ADO.NET

Entity Framework

Dapper

Miniprofiler

CQRS

Event Store

RabbitMQ

eBay Inc. confidential

Where we ended

36

eBay Inc. confidential

Q&A

37

eBay Inc. confidential 38