Beyond Hyper-growth: Tackling scalability challenges on Android

In just over a year, our Android team exploded from 4 people to 34!
In this talk we will go through the challenges faced by Android engineers when dealing with fast growing teams. Most importantly, we are going to showcase scalable and sustainable solutions.
We'll tackle questions like: What were our biggest technical challenges? How did we prevent bottlenecks? How did we maintain consistency and not block creativity? What were our biggest mistakes and how did we solve them?
By the end of this talk you will have a better understanding of the problems scaling an Android team, how to tackle them and how to create a safe and productive environment.

Transcript

1. Beyond hyper-growth Beyond hyper-growth
2. Beyond hyper-growth Beyond hyper-growth Tackling scalability challenges on Android Daniel Horowitz
3. Hyper-growth?
4. –Slack bot , slack analytics “N26 slack users grew from less than 200 to more than 2k in 3 years”
5. Hyper-growth on android?
6. “The android team grew 500% in 1.5 years”
7. “The android team grew 500% in 1.5 years” # of android devs 2014 2016 2018 2020 4 13 27 34
8. How can 30+ devs work in the same code base?
9. :app
10. :app
11. :app Feature A Feature B Feature C Core Login Architecture Database Dependency Injection Logging Feature n Feature D …
12. Monolith
13. Monolith Long build times Hidden dependency and coupling between features No clear ownership for features No awareness of changes
14. Inspiration from micro-services Breaking up the monolith
15. Monolith
16. Monolith Microservices Highly maintainable and testable Loosely coupled and independently deployable Organised around business capabilities Clear ownership
17. Cross functional teams Explore
18. Cross functional teams Explore
19. Cross functional teams Explore Spaces Actions Feeds …
20. :app Explore Spaces Actions Feeds … user-identity bank-account … Contacts Pin-input … Analytics NXD Security Navigation Networking Forge26
21. Modularisation in practice Reduce build times :app Explore Spaces Actions Feeds … user-identity bank-account … Contacts Pin-input … Analytics NXD Security Navigation Networking Forge26 //Parallelise builds for multiple modules //gradle.properties org.gradle.parallel=true
22. Running tasks in parallel ./gradlew assembleDebug Modularisation in practice
23. Standalone features Modularisation in practice
24. Standalone features
25. Short build times Clear ownership Loosely couple Possibility of Dynamic delivery Standalone features
26. Dynamic delivery :app Explore Spaces Actions Feeds KYC Dynamic feature
27. KYC Install on demand Downloads N26 Reduced apk size Sign up Continue to N26 Home KYC Dynamic feature Dynamic delivery
28. Scalability
29. Scalability
30. Scalability Quality Observability Independency Consistency
31. Quality Testing - Unit - Espresso - E2E Automation Code reviews
32. Testing Every feature should be unit tested - More than 8k unit tests UI tests for ensuring behaviour - More than 400 Espresso tests E2E for happy paths Testing
33. Release trains PRs triggers quality tasks - Tests - Lint and style checks Automation of manual tasks - Bootstrap features - Run UI tests on CI - Feature migration - Git hooks Automation
34. Code Reviews Avoid style checks Limit PR size Code ownership
35. Scalability Quality Observability Independency Consistency
36. Independency Modularisation Cross functional teams Feature flags Code freedom
37. Independency Dedicated pipeline per feature
38. Scalability Quality Observability Independency Consistency
39. Observability Build times Apk/Bundle size PRs Test duration
40. Observability Pull requests
41. Observability
42. Observability Google play
43. Observability Sonarqube
44. Scalability Quality Observability Independency Consistency
45. Consistency NXD Server driven UI
46. NXD Glossary app
47. listOf( NXD In practice
48. SectionHeader("Transactions"), listOf(
49. SectionHeader("Transactions"), listOf( SubSectionHeader(“Today"),
50. SectionHeader("Transactions"), listOf( SubSectionHeader(“Today"), TransactionContainer( "From Main Account", " to Home", Money(BigDecimal(5), Euro)), TransactionContainer( "From Main Account", "Last one ... ", Money(BigDecimal(4.50), Euro)), TransactionContainer( "From Main Account", "Just one more ", Money(BigDecimal(5), Euro)), TransactionContainer( "From Main Account", "Money for drinks!", Money(BigDecimal(5), Euro))))
51. Presentation gateways Responses contains elements to be rendered Keep consistency throughout different platforms Server driven UI
52. Server driven UI Server driven UI Polymorphic API response Map into data models UI Rendering Carousel Section ImageCard Rendering framework
53. Server driven UI Server driven UI API response Map to data models UI Rendering Carousel ImageCard Rendering framework Section
54. Server driven UI API response Map to data models UI Rendering SimpleCard ImageCard Rendering framework Section Server driven UI
55. Server driven UI Server driven UI
56. Server driven UI Server driven UI Be mindful of API design Versioning and backwards compatibility There’s no silver bullet
57. Beyond hyper-growth Thank you