1. Is it hard to build a service for 100M user? Short answer – yes

2. /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

3. /dev/viber Some numbers… 100M registered users 2.5B text, 1.7B voice minutes monthly 50 employees in Belarus, about 120 worldwide

4. /dev/viber What do we do? Free calls, messages and group messages (more coming!) Your number is your “user id” Always On…

5. /dev/viber Why Viber became popular People love to get something for free First one to do it “right” It’s purple :)

6. /dev/viber Reception 1M after 3 days Very high growth ratio Give us more (platforms, features) – “Where is the Blackberry version?”

7. /dev/viber What we saw as a result? PROBLEMS!!!

8. /dev/viber Building a service that can handle 100M users in 1.5 years is difficult. Really.

9. /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.

10. /dev/viber Scaling “Scaling is replacing all components of a car while driving it at 100MPH” [Mike Krieger, Instagram]

11. /dev/viber When developers say “fully scalable” they don’t really mean it…

12. /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

13. /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

14. /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

15. /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

16. /dev/viber Say goodbye to life You are always in the office Sometime the office is at home Sometime at the beach Sometime...

17. /dev/viber Shit happens Stuff will break Stay cool and fix Communicate with your users

18. /dev/viber Monitoring Collect tons of stats Look at them Look at them again Trending matters. Things don’t just happen.

19. /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

20. /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)

21. /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…

22. /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)

23. /dev/viber iOS Device Breakdown 6 users registered with iPhone 5

24. /dev/viber iOS versions breakdown

25. /dev/viber Mobile upgrade speed Desktop application upgradeMobile application upgrade

26. /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

27. /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

28. /dev/viber Lessons learned Always plan for success Monitor your system Hire best people It’s VERY REWARDING! hr.blr@viber.com

29. /dev/viber Questions?