Building Scalable Mobile Projects: Fast Builds, High Reusability and Clear Ownership

Every successful project eventually faces the challenges of scaling: an ever-growing codebase, an increasing number of contributors, and rising complexity. Without proper measures, this can lead to slow build times, a cluttered codebase, maintenance difficulties, code duplication, and even dead code—ultimately jeopardizing the company’s ability to deliver value.

Fortunately, there are proactive strategies maintainers can adopt to ensure the project remains scalable and resilient. In this talk, we’ll explore how to structure a mobile codebase to support rising product complexity and accommodate tens of engineers making hundreds of daily commits while maintaining super fast build times, high reusability, and clear ownership.

Transcript

1. Building Scalable Mobile Projects Fast Builds, High Reusability and Clear Ownership cyrilmo tt
2. Abstract Every successful project eventually faces the challenges of scaling: an ever-growing codebase, an increasing number of contributors, and rising complexity. Without proper measures, this can lead to slow build times, a clu ffi Fortunately, there are proactive strategies maintainers can adopt to ensure the project remains scalable and resilient. In this talk, we’ll explore how to structure a mobile codebase to support rising product complexity and accommodate tens of engineers making hundreds of daily commits while maintaining super fast build times, high reusability, and clear ownership.
3. Once upon a time…
4. Once upon a time… My awesome app
5. Once upon a time… My awesome app
6. Once upon a time… My awesome app
7. Once upon a time… My awesome app
8. Once upon a time… My awesome app Feature 1 Feature 3 Feature 4 Feature 2 Feature 5 Feature 7 Feature 8 Feature 6
9. Once upon a time… My awesome app
10. Building Scalable Mobile Projects
11. Building Scalable Mobile Projects
12. Backward compatibility Scalability Security Observability Fast build times Quality Cost e ff i ciency Testability Fast delivery Reusability Compliance Scalability Collaboration What to optimize for? Static analysis Code locality User experience Encapsulation Customisable delivery Performance Searchability Disaster recovery Flexibility Internationalization Knowledge sharing Strict visibility control Interoperability Developer experience Clear ownership Automation Maintainability
13. Backward compatibility Scalability Security Observability Fast build times Quality Cost e ff i ciency Testability Fast delivery Reusability Compliance Scalability Collaboration What to optimize for? Static analysis Code locality User experience Encapsulation Customisable delivery Performance Searchability Disaster recovery Flexibility Internationalization Knowledge sharing Strict visibility control Interoperability Developer experience Clear ownership Automation Maintainability 😱
15. Context is key
16. Context is key amo example Super competitive consumer social ecosystem
17. Context is key amo example Speed of execution and ability to adapt is vital Super competitive consumer social ecosystem
18. Context is key amo example Ton of features reused in 1 or multiple apps Speed of execution and ability to adapt is vital Super competitive consumer social ecosystem
19. Context is key Ton of features reused in 1 or multiple apps Speed of execution and ability to adapt is vital Super competitive consumer social ecosystem amo example
20. Backward compatibility Scalability Security Observability Fast build times Quality Cost e ff i ciency Testability Fast delivery Reusability Compliance Scalability Collaboration What to optimize for? Static analysis Code locality User experience Encapsulation Customisable delivery Performance Searchability Disaster recovery Flexibility Internationalization Knowledge sharing Strict visibility control Interoperability Developer experience Clear ownership Automation Maintainability
21. Backward compatibility Scalability Security Observability Fast build times Quality Cost e ff i ciency Testability Fast delivery Reusability Compliance Scalability Collaboration What to optimize for? Static analysis Code locality User experience Encapsulation Customisable delivery Performance Searchability Disaster recovery Flexibility Internationalization Knowledge sharing Strict visibility control Interoperability Developer experience Clear ownership Automation Maintainability
22. 1 Fast build times
23. 1 Fast build times 2 Reusability
24. 1 Fast build times 2 3 Clear ownership Reusability
25. 1 Fast build times 2 3 Clear ownership Reusability
26. The main solution to all these aspects is… Modularization
27. The main solution to all these aspects is… Modularization But only if done the proper way…
28. Maximize cohesion Minimize coupling
29. Common pitfalls Modularising by layer vs by feature Creating too fi ne/coarse-grained modules Having overly complex API surface Depending on too many modules Exposing overly large feature set
30. A tool to transform source code into executable programs Build System bɪld sɪs.təm/ /
31. Build System bɪld sɪs.təm/ / Modern mɑː.dɚn A tool to coordinate the execution of a reversed topological sort of a directed acyclic graph of actions.
32. A B D E F C H G
33. A B D E F C H G
34. A B D E F C H G
35. A B D E F C H G
36. A B D E F C H G
37. A B D E F C H G
38. A B D E F C H G
39. A B D E F C H G
40. A B D E F C H G Possible order of actions
41. A B D E F C H G Possible order of actions C F H
42. A B D E F C H G Possible order of actions C F H
43. A B D E F C H G Possible order of actions C F H B E
44. A B D E F C H G Possible order of actions C F H B E
45. A B D E F C H G Possible order of actions C F H B E D
46. A B D E F C H G Possible order of actions C F H B E D
47. A B D E F C H G Possible order of actions C F H B E D
48. A B D E F C H G Possible order of actions Visual top to bo tt C F H B E D
49. A B D E F C H G Possible order of actions C F H B E D
50. A B D E F C H G Possible order of actions D C F H B E
51. A B D E F C H G Possible order of actions D C F H B E Most edges fi
52. A B D E F C H G
53. A B D E F C H G 2 2 6 2 4 1
54. C F H B E D 2 4 2 6 1 2 #1 #2 Workers 0 1 2 3 4 5 6 7 8 9 10 11 Unit of time A B D E F C H G
55. C F H B E D 2 4 2 6 1 2 #1 #2 Workers 0 1 2 3 4 5 6 7 8 9 10 11 Unit of time A B D E F C H G
56. H C F B E D 2 4 2 6 1 2 Workers #3 #2 #1 0 1 2 3 4 5 6 7 8 9 10 11 Unit of time A B D E F C H G
57. A B D E F C H G 2 3 6 2 4 1
58. A B D E F C H G 2 3 6 2 4 1
59. A B D E F C H G
60. A Outputs Inputs 5
61. A Inputs Outputs 5
62. A Inputs Outputs 5
63. A Inputs Outputs 5
64. A Inputs Outputs 5
65. A Inputs Outputs 5
66. A Inputs Outputs 5
67. A Inputs Outputs 5
68. A Inputs Outputs 5
69. A 5
70. A B D E F C H G
71. A B D E F C H G
72. A B D E F C H G
73. A B D E F C H G
74. A B D E F C H G
75. Correctly sized compilation units The unwavering path
76. Correctly sized compilation units Compilation avoidance at all cost The unwavering path
77. Correctly sized compilation units Compilation avoidance at all cost “Frequency of change” aware DAG The unwavering path
78. Correctly sized compilation units Compilation avoidance at all cost “Frequency of change” aware DAG The unwavering path Breadth-oriented DAG
79. Correctly sized compilation units Breadth-oriented DAG Compilation avoidance at all cost “Frequency of change” aware DAG The unwavering path
80. Structuring a codebase around the code locality principle
81. monorepo ├── android ├── bazel ├── ci ├── docs ├── ios ├── rs ├── third_party ├── tools └── web
82. monorepo ├── android │ ├── apps │ ├── build-logic │ ├── components │ ├── development │ ├── distribution │ ├── documentation │ ├── foundation │ ├── platform │ └── tools └── …
83. Foundation 4 module categories Platform Components Apps
84. monorepo ├── android │ ├── … │ ├── components │ │ ├── settings │ │ │ ├── api │ │ │ ├── bindings │ │ │ ├── core │ │ │ ├── core-bindings │ │ │ └── lib │ │ └── … │ └── … └── …
85. Types of modules api lib bindings core core-bindings sample apps - amo speci fi - amo speci fi
86. androidx composex coroutinesx coilx … Foundation analytics navigation bug-reporting uni fi … Platform api amplitude amplitude-bindings api shake shake-bindings api lib bindings api lib bindings
87. androidx composex coroutinesx coilx … Foundation analytics navigation bug-reporting uni fi ed-map … Platform api amplitude amplitude-bindings api shake shake-bindings api lib bindings api lib bindings best-friend identity pro fi now-playing … se tt Components api lib bindings api lib bindings api lib bindings api lib bindings api lib bindings
88. androidx composex coroutinesx coilx … Foundation best-friend identity pro fi le now-playing … se tt ings Components api lib bindings api lib bindings api lib bindings api lib bindings api lib bindings analytics navigation bug-reporting uni fi ed-map … Platform api amplitude amplitude-bindings api shake shake-bindings api lib bindings api lib bindings location location-instant gra f gra ff … Apps
89. androidx composex coroutinesx coilx … Foundation best-friend identity pro fi le now-playing … se tt ings Components api lib bindings api lib bindings api lib bindings api lib bindings api lib bindings location location-instant gra f gra ff -instant … Apps analytics navigation bug-reporting uni fi ed-map … Platform api amplitude amplitude-bindings api shake shake-bindings api lib bindings api lib bindings
90. androidx composex coroutinesx coilx … Foundation best-friend identity pro fi le now-playing … se tt ings Components api lib bindings api lib bindings api lib bindings api lib bindings api lib bindings location location-instant gra f gra ff -instant … Apps analytics navigation bug-reporting uni fi ed-map … Platform api amplitude amplitude-bindings api shake shake-bindings api lib bindings api lib bindings
91. androidx composex coroutinesx coilx … Foundation best-friend identity pro fi le now-playing … se tt ings Components api lib bindings api lib bindings api lib bindings api lib bindings api lib bindings location location-instant gra f gra ff -instant … Apps analytics navigation bug-reporting uni fi ed-map … Platform api amplitude amplitude-bindings api shake shake-bindings api lib bindings api lib bindings
92. androidx composex coroutinesx coilx … Foundation best-friend identity pro fi le now-playing … se tt ings Components api lib bindings api lib bindings api lib bindings api lib bindings api lib bindings location location-instant gra f gra ff -instant … Apps analytics navigation bug-reporting uni fi ed-map … Platform api amplitude amplitude-bindings api shake shake-bindings api lib bindings api lib bindings
93. androidx composex coroutinesx coilx … Foundation best-friend identity pro fi le now-playing … se tt ings Components api lib bindings api lib bindings api lib bindings api lib bindings api lib bindings location location-instant gra f gra ff -instant … Apps analytics navigation bug-reporting uni fi ed-map … Platform api amplitude amplitude-bindings api shake shake-bindings api lib bindings api lib bindings
94. androidx composex coroutinesx coilx … Foundation best-friend identity pro fi le now-playing … se tt ings Components api lib bindings api lib bindings api lib bindings api lib bindings api lib bindings location location-instant gra f gra ff -instant … Apps analytics navigation bug-reporting uni fi ed-map … Platform api amplitude amplitude-bindings api shake shake-bindings api lib bindings api lib bindings
95. androidx composex coroutinesx coilx … Foundation best-friend identity pro fi le now-playing … se tt ings Components api lib bindings api lib bindings api lib bindings api lib bindings api lib bindings location location-instant gra f gra ff -instant … Apps analytics navigation bug-reporting uni fi ed-map … Platform api amplitude amplitude-bindings api shake shake-bindings api lib bindings api lib bindings
96. Foundation Components Apps Platform androidx composex coroutinesx coilx … best-friend identity pro fi now-playing … se tt api lib bindings api lib bindings api lib bindings api lib bindings api lib bindings location location-instant gra f gra ff … analytics navigation bug-reporting uni fi … api amplitude amplitude-bindings api shake shake-bindings api lib bindings api lib bindings
97. androidx composex coroutinesx coilx … best-friend identity pro fi now-playing … se tt api lib bindings api lib bindings api lib bindings api lib bindings api lib bindings location location-instant gra f gra ff … analytics navigation bug-reporting uni fi … api amplitude amplitude-bindings api shake shake-bindings api lib bindings api lib bindings Foundation Components Apps Platform
98. Foundation Components Apps Platform androidx composex coroutinesx coilx … best-friend identity pro fi now-playing … se tt api lib bindings api lib bindings api lib bindings api lib bindings api lib bindings location location-instant gra f gra ff … analytics navigation bug-reporting uni fi … api amplitude amplitude-bindings api shake shake-bindings api lib bindings api lib bindings
99. Foundation Components Apps Platform androidx composex coroutinesx coilx … best-friend identity pro fi now-playing … se tt api lib bindings api lib bindings api lib bindings api lib bindings api lib bindings location location-instant gra f gra ff -instant … analytics navigation bug-reporting uni fi … api amplitude amplitude-bindings api shake shake-bindings api lib bindings api lib bindings
100. Foundation Components Apps Platform androidx composex coroutinesx coilx … best-friend identity pro fi now-playing … se tt api lib bindings api lib bindings api lib bindings api lib bindings api lib bindings location location-instant gra f gra ff … analytics navigation bug-reporting uni fi … api amplitude amplitude-bindings api shake shake-bindings api lib bindings api lib bindings
101. Foundation Components Apps Platform androidx composex coroutinesx coilx … best-friend identity pro fi now-playing … se tt api lib bindings api lib bindings api lib bindings api lib bindings api lib bindings location location-instant gra f gra ff -instant … analytics navigation bug-reporting uni fi … api amplitude amplitude-bindings api shake shake-bindings api lib bindings api lib bindings
102. Foundation Components Apps Platform androidx composex coroutinesx coilx … best-friend identity pro fi now-playing … se tt api lib bindings api lib bindings api lib bindings api lib bindings api lib bindings location location-instant gra f gra ff … analytics navigation bug-reporting uni fi … api amplitude amplitude-bindings api shake shake-bindings api lib bindings api lib bindings
103. Foundation Components Apps Platform androidx composex coroutinesx coilx … best-friend identity pro fi now-playing … se tt api lib bindings api lib bindings api lib bindings api lib bindings api lib bindings location location-instant gra f gra ff -instant … analytics navigation bug-reporting uni fi … api amplitude amplitude-bindings api shake shake-bindings api lib bindings api lib bindings
104. Ability of a so ff Reusability /rijuːzəbɪləti/
105. dependencies { implementation( projects.components.settings.bindings ) } android/apps/location/build.gradle.kts
106. @Provides fun provideSettingsConfiguration(): SettingsConfiguration = SettingsConfiguration( socialMedia = listOf( SocialMedia.Instagram( “bumpbyamo", R.string.socialMedia_instagram), ), ), ) dependencies { implementation( projects.components.settings.bindings ) } android/apps/location/src/main/LocationAppModule.kt android/apps/location/build.gradle.kts and optionally…
107. dependencies { implementation( projects.components.avatar.bindings ) } android/apps/location/build.gradle.kts
108. dependencies { implementation( projects.components.avatar.bindings ) } android/apps/location-instant/build.gradle.kts dependencies { implementation( projects.components.avatar.bindings ) } android/apps/location/build.gradle.kts
109. dependencies { happyImplementation( projects.components.superSecretNewFeature.bindings ) } android/apps/location/build.gradle.kts dependencies { implementation( projects.components.avatar.bindings ) } android/apps/location-instant/build.gradle.kts dependencies { implementation( projects.components.avatar.bindings ) } android/apps/location/build.gradle.kts
110. dependencies { happyImplementation( projects.components.superSecretNewFeature.bindings ) } android/apps/location/build.gradle.kts dependencies { implementation( projects.components.avatar.bindings ) } android/apps/location-instant/build.gradle.kts dependencies { implementation( projects.components.avatar.bindings ) } android/apps/location/build.gradle.kts
111. The responsibility and accountability taken by individuals or teams for speci fi Ownership /oʊ.nɚ.ʃɪp/
112. GitHub CODEOWNERS
119. No solutions is perfect It is a matter of concessions
120. Thank You! Any questions?