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Mobile Product Engineering

Mobile Product Engineering

A talk I gave at SaaS Engineering (https://www.youtube.com/channel/UCPNcEyOQD2-X2YB6akbr-xA) on how to build a better mobile product engineering team.

Arnav Gupta

June 09, 2022
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  1. Mobile Product Engineering
    Arnav Gupta

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  2. Disclaimer: Personal Bias
    Past experiences which form my opinion
    ● 1.5 yrs : Platform Team Lead & Mobile Engineering Lead @ Zomato
    ● 1.5 yrs : Lead Engineer (Android) @ Target
    ● 10+ years mostly native Android
    Advice most suited to
    ● Scaleups / Large tech teams
    ● Ecom, B2C, large DAU (1M+) products

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  3. Outline
    Engineering
    Org Design
    Process
    Testability*

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  4. Engineering
    ‘scale’ is different
    modularisation
    3rd party libraries
    navigation, deeplinks, state

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  5. ‘scale’ is different
    ● device, OS, version fragmentation
    ● low bandwidth, low storage size, low RAM devices
    ○ content consumption apps: frequent customer complaints = data usage
    ○ in a competitive field: app size ∝ uninstall rate
    ● txns/day or API hits per sec are STILL important; why ?
    ○ good caching on frontend, helps backend teams
    ○ lots of ‘scale’ mitigation happens on frontend (eg: exponential backoff)
    ○ frontend can DDoS backend

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  6. modularisation

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  7. 3rd party libraries
    ● 1 line of code you don’t own = 1 line of risk you undertake
    ● even the biggies can fail you
    ○ Google Maps SDK bug: 20M+ users, 96% of top 1000 apps affected
    ○ Facebook Login SDK bug: 10M+ users, 80% of top 1000 apps affected
    ● include prebuilt vs add as source
    ○ build-time hit vs ability to self-fix
    ○ security considerations
    ○ CI able to pull 3rd party libs

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  8. deeplinks, navigation, state
    ● the closer your navigation graph is to a pure state machine the
    better you’ll sleep at night
    ● deeplinks should be idempotent, like GET requests, and just work™
    zoma.to/r/135 https://zomato.com/restaurants/ncr/gulati
    zoma.to/u/34
    fb://user/arnav https://facebook.com/@arnav

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  9. deeplinks, navigation, state

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  10. Org Design
    to QA or not to QA
    pod-wise teams
    platform team?

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  11. to QA or not to QA

    We can solve any problem by introducing an extra level of indirection

    - David J Wheeler to Butler Lampson

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  12. to QA or not to QA

    We can solve any problem by introducing an extra level of indirection…
    … except the problem of too many levels of indirection

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  13. to QA or not to QA
    ● PMs do have ability to toggle flags on DB, install apps, capture logs
    ● PMs will do “strategy”, cannot spend time on run-of-the-mill testing
    and operational tasks
    ● Engineers do not test thoroughly, we need a QA to be bulletproof
    ● Testing features need co-ordinating between frontend + mobile +
    backend engineers, QA can coordinate with all of them better
    ● We have compliance reasons
    ● Why do other companies have QA teams then?

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  14. pod-wise teams
    start when > 5 team size
    OK if 1 pod = 1 person
    1 pod owns 2 modules ✅
    2 pods work on 1 module ❌
    split pods per business domain

    split pods per tech function ❌

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  15. platform team ?
    do you need one?
    platform teams clean up after
    feature pods ❌
    platform teams built libs that
    feature teams use ✅
    platform teams are responsible for
    reliability/performance ❌
    platform teams create tools +
    monitoring for better app perf ✅
    platform teams do releases ❌
    platform teams own CI/CD infra ✅

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  16. Process
    trunk-based development
    release train
    build versioning
    1 ticket = 1 branch = 1 build = 1
    signoff

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  17. trunk-based development & release train

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  18. trunk-based development & release train

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  19. trunk-based development & release train

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  20. build versioning
    ● what is the APK version of the following apps you use on your
    phone ?
    ○ Google Maps
    ○ Google Pay / PhonePe / PayTM
    ○ Swiggy / Zomato
    ● product features ↔ version number pairing not needed
    ● 2022.12 (week num), or 2022.5.1-5472 (YMD+buildnum)
    ● v10 of Android = v10 of iOS has same features - why ?
    ● control feature rollout via
    ○ server side feature flags
    ○ API headers

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  21. 1 ticket = 1 branch = 1 build = 1 signoff
    ● 1 short-lived branch created for 1 JIRA ticket
    ○ scope your work so that this is < 1 week of work
    ● Use Firebase Test Labs + Test Flight for CD-to-employees
    ● PM/Design/Business should be able to “install a ticket id”
    ● Single place to for all stakeholders to -
    ○ get build for the ticket
    ○ discuss design / specs / requirements
    ○ sign off on release

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  22. Testability
    unit test vs integration test
    snapshot tests?
    debug drawer & feature flags
    enabling manual testing

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  23. unit tests vs integration tests
    ● tooling, difficulty and build time of integration tests
    ● what are you testing ?
    ○ input/output of function?
    ○ business logic?
    ○ state machine?
    ● mocking vs faking
    ○ can we test by hitting real APIs ?

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  24. snapshot testing
    do you need it ?
    fragility & flakiness
    keeping up with design iteration speed
    accessibility tests

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  25. debug drawer & feature flags
    ● API server domain switching
    ● A/B test (assuming test/control group)
    ● Assume user id
    ● Feature flag local overrides
    ● Dev Tool enable/disable
    ○ profiling
    ○ mem-leak catching
    ○ event / logs / trace capturing

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  26. enabling manual testing

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  27. enabling manual testing

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  28. good reads

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  29. blogs
    developer.squareup.com
    eng.uber.com/category/articles/mobile
    slack.engineering
    zomato.com/blog/category/technology
    blog.hotstar.com/tagged/engineering

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