Is it hard to build a service for
100M user?
Short answer – yes 
/dev/viber
What would you do if you had
1,000,000 users after 3 days?
1. Run away
2. Get drunk
3. Pray
4. All of the above
/dev/viber
Some numbers…
• 100M registered users
• 2.5B text, 1.7B voice minutes monthly
• 50 employees in Belarus, about 120
worldwide
/dev/viber
What do we do?
• Free calls, messages and group messages
(more coming!)
• Your number is your “user id”
• Always On…
/dev/viber
Why Viber became popular
• People love to get something for free
• First one to do it “right”
• It’s purple :)
/dev/viber
Reception
• 1M after 3 days
• Very high growth ratio
• Give us more (platforms, features)
– “Where is the Blackberry version?”
/dev/viber
What we saw as a result?
PROBLEMS!!!
/dev/viber
Building a service that can handle
100M users in 1.5 years is difficult.
Really.
/dev/viber
Why problems?
• More usage - more load on backend
• More platforms:
– More development
– Can’t deliver all features on all platforms at the
same time.
/dev/viber
Scaling
“Scaling is replacing all components of a car while
driving it at 100MPH” [Mike Krieger, Instagram]
/dev/viber
When developers say “fully scalable”
they don’t really mean it…
/dev/viber
Backend
• Got to 1M connected users in less than 2
weeks
• Used Amazon EC2, but still you have to design
for scalability
• Started from 30 servers (and we thought it
was a LOT)
• So we started to rewrite
/dev/viber
Why is it so hard?
•
•
•
•
•
•
Address books (100M)
Reverse address entries (3B)
300,000 data requests per second
Active dataset 1.5TB
15-20M concurrent connected users (TCP)
Over 100,000 concurrent phone calls
/dev/viber
How to handle all the data
•
•
•
•
NoSQL (MongoDB, Redis)!
Sharding
MongoDB uses auto-sharding but it’s slow
Simple in-memory solutions require lot of
work
/dev/viber
We are our biggest enemy
• A small mistake on a mobile client can lead to
a massive DDOS
• One bug in Android client = 100 times load on
backend
/dev/viber
Say goodbye to life
•
•
•
•
You are always in the office
Sometime the office is at home
Sometime at the beach
Sometime...
/dev/viber
Shit happens
• Stuff will break
• Stay cool and fix
• Communicate with your users
/dev/viber
Monitoring
•
•
•
•
Collect tons of stats
Look at them
Look at them again
Trending matters. Things don’t just happen.
/dev/viber
Backend now
• Constantly rewriting and optimizing
• Runs on 300 servers (and we think it's not too
much)
• Using and improving open source software
/dev/viber
Backend - technologies
•
•
•
•
•
Proprietary front-end servers (C++, really fast)
Redis – in memory NoSQL, fast
MongoDB – persistent NoSQL, not so fast
MySQL – registrations, pretty slow
Always looking for alternatives
(CouchBase, DynamoDB, etc)
/dev/viber
Platforms
• Users wants to communicate with their
friends, but they keep buying different phones
• Started from iOS and had Android community
bashing us for a year
• Now: iOS, Android, Blackberry,
WindowsPhone 7
• More coming…
/dev/viber
Client challenges - iOS
• Support numerous iOS versions (we’re finally
dropping support for iOS 3)
• Support several device type (3G, 3GS, 4, 4S)
• Need to react very fast (iOS upgrade)!
• Hard to test on large scale (no beta testing,
although there is a one-time solution)
/dev/viber
iOS Device Breakdown
3.60%
7.16%
6%
36.60%
11.57%
iPhone 4S
iPhone 4
iPhone 3GS
iPhone 3G
34.77%
iPod
iPad
6 users registered with iPhone 5
/dev/viber
iOS versions breakdown
1.10%
13.90%
iOS3
iOS4
84.80%
iOS5
/dev/viber
Mobile upgrade speed
Desktop application upgrade
Mobile application upgrade
/dev/viber
Client challenges - Android
• Devices/platform fragmentation (we saw
more then ??? devices)
• Lot of sound-related bugs caused by it
• Different screens and device caps
• APIs not always work as documented and not
always documented
/dev/viber
Client challenges - voice & video
infrastructure
•
•
•
•
•
Have to choose/write a proper engine
Now we are using and modifying WebRTC
Has to work smoothly on mobile devices
3G is a pain
Has to optimize for several platforms
/dev/viber
Lessons learned
•
•
•
•
Always plan for success
Monitor your system
Hire best people
It’s VERY REWARDING!
hr.blr@viber.com
/dev/viber
Questions?