This document discusses developing mobile apps for performance. It emphasizes that user perceived latency, stability, and battery life matter most to users. A key performance indicator is cold app launch time, which should be under 2 seconds to keep users happy. Measuring app performance is challenging as it needs to account for different devices, networks, and conditions. The document recommends reducing network calls to load the home screen faster by fetching content in the user's viewpoint with a single endpoint and network call.

1. Developing Mobile Apps for
Performance
Swapnil Patel, Director of Software Engineering (Mobile),
Verizon Media
February 21st, 2019

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Users are complaining...but I did my job!
● I’m losing my DAUs but the app works perfectly.
● Performance tests passed 100% but user feedback is negative.
● Are we measuring performance KPIs correctly?

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Product teams...

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Security Engineers…

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What matters to users?

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● Latency (User perceived)
● Stability
● Battery
App Performance

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User perceived latency: Cold app launch

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Why is it taking so
long to launch
content?

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Cold app launch...keep it under 2000ms!
< 1500 ms I love this app!
> 1500 ms && < 5000 ms It should work!
> 5000 ms I’m done with this app!

10. Users may stop using your app
without sharing any negative
feedback

11. Measuring App Launch Performance

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Measuring app performance isn’t easy
● Hard to test and simulate real world scenarios
○ Controlled environment
○ High-end devices
○ Test hardware on low latency networks - test machines and
devices
○ Did you simulate 3G/4G network and real-world conditions?
● Needs continuous auditing
○ Different network bandwidth levels
○ Device capabilities
○ Regions or geo-locations

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App performance KPI: Cold App
Launch (iOS)
Credit: Devrim Tufan (Verizon Media), Scott Tury (Verizon Media)

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App performance KPI: Cold App
Launch (Android)
We want to report cold_start_display = Δdisplay with breakdowns
cpuElapsedTime appCreateDelta appCreateActCreateDelta actCreateStartDelta actStartResumeDelta actResumeDisplayDelta
Most apps report cold_start_* = Δd1 + Δd2 + Δd3
Credit: Devrim Tufan (Verizon Media), Scott Tury (Verizon Media)

15. Fine-tuning App Launch Performance

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What’s one thing I wish I knew before?
Fetch content in the
user’s viewpoint with a
single end point.

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What’s one thing I wish I knew before?
Fetch content in the
user’s viewpoint with a
single end point.
Reduce the number of
network calls to load
your home screen
faster.

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○ App cache
○ Background prefetch
○ Silent notifications
○ Network layer optimizations
○ User feedback (spinners,
animations…)
Nice to have…

19. Fetch content in the user’s viewpoint
with a single end-point, single
network call.

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Thanks!

21. Reach out
Swapnil Patel
Director of Software Engineering, Verizon Media
swapatel@verizonmedia.com
@patelsince1981
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