Scaling an app to 175 million users

CocoaHeads Ukrain, Kyiv, 4th of March 2017

SoundCloud's mobile apps fast became their primary listening platform. This talk will highlight the biggest challenges SoundCloud iOS team faced scaling their app and the team to where they are today and the biggest things they’ve gotten right and wrong in the process.

Matej will discuss what were the high level ideas that allowed the team to scale, but will also dive deep and share some practical examples that any growing team can adapt.

Transcript

2. @skavt matej@soundcloud.com Scaling an app 
 to 175 million users Kyiv, March 2017
3. Matej Balantič Engineering Manager, Core Clients Coding professionally for 10 years Started with backend / PHP 5 years ago —> mobile/iOS Experimenting with management for the last 6 months Core Clients = build tools & libraries to make client engineers more productive
5. SoundCloud iOS app history Show project name and launch date 2008 2009 2010 2011 2012 2013 2014 2016 2015 2016 2017 Milestone iPhone app released Agency Team of 6 Team of 15 1 MIO 175 
 MIO 10 MIO Release of rewrite
6. IOS TEAM TODAY
7. Team 4 Team 3 Core Team 2 Team 1 Team 1 Team 2 Core Team 3 Team 4 iOS collective 5 independent teams 15 iOS engineers 2 locations Plans for 2017: double the team
8. How busy is it?
9. IOS PROJECT TODAY
12. Test & Build Clean build time =~ 15 minutes 13k unit tests that run ~5 minutes 400 acceptance tests that run ~15 minutes CI pipeline = 40 macOS nodes on 20 Mac Minis
14. SUSTAINABLE GROWTH
15. Sustainable growth
16. Sustainable growth
17. Sustainable growth Iteration [ GOOD ] Productivity [ CHEAP ] Onboarding [ FAST ]
18. PRODUCTIVITY 1
19. TEAM STRUCTURE
20. Team structure The challenge
21. Team structure The idea
22. Team structure The reality
23. Team structure The reality
24. Code authors Temporal relationship between authors
25. BUILD TIMES
27. - myself Shaving off 1 minute build time saves some time and tons of frustration
29. Track Search Player Project structure
30. Application Project structure Track Search Player
32. Framework Framework Project structure Framework Track Search Player Application
33. Framework Framework Project structure Framework Track Search Player Application
34. Framework Framework Project structure Framework Track Search Player Application
35. Framework Framework Project structure Framework Track Search Player Application
36. Project structure Framework Framework Framework Track Search Player Application
37. Project structure DEFINITIONS FRAMEWORK Framework Framework Framework Track Search Player Application
38. Project structure DEFINITIONS FRAMEWORK Framework Framework Framework Track Search Player Application
39. Project structure DEFINITIONS FRAMEWORK Framework Framework Framework Track Search Player Application
40. Project structure DEFINITIONS FRAMEWORK Framework Framework Framework Track Search Player Application
41. Project structure DEFINITIONS FRAMEWORK Framework Framework Framework Track Search Player Application
42. ONBOARDING 2
43. July interview September joined the team December becomes productive Case study: 3 months to productivity
44. Self-onboarding
45. Playgrounds
46. Playgrounds
47. ITERATION 3
48. TRUNK BASED DEVELOPMENT
49. alwaysagileconsulting.com A version control strategy in which developers commit their changes to the shared trunk of a source code repository with minimal branching Trunk based development
50. Trunk based development
51. Trunk based development
52. FEATURE FLAGS
53. { "development": { "dev_important_task": { "enabled": true, "description": "Super new experimental feature" }, "dev_some_other_task": { "enabled": true, "description": "Some other not so experimental feature" } }, "production": { "dev_important_task": { "enabled": false
 } } } 1. Add feature to JSON
54. 2. Run script
55. 2. Run script
56. public class ImportantService { public func importantTask() { guard FeatureFlagService.isDevImportantTaskEnabled() else { return } doImportantTask() } // MARK: Private private func doImportantTask() { // ... } } 3. Use in code
57. public class ImportantService { public func importantTask() { guard FeatureFlagService.isDevImportantTaskEnabled() else { return } doImportantTask() } // MARK: Private private func doImportantTask() { // ... } } 3. Use in code
58. 4. Profit
62. . Slides
 bit.ly/kyiv-cocoa @skavt
 matej@soundcloud.com THANK YOU! Questions?
63. . Framework Oriented Programming
 http://frameworkoriented.io CodeScene
 https://codescene.io REFERENCES