Been shipping production mobile apps for 5 years. everyone optimizes startup time to death. we spent 3 months cutting our cold start from 2.8s to 1.2s. user retention moved 0.3%. then we fixed onboarding flow friction in 2 days. retention went up 8%.

the math is simple: 90% of your users aren't doing cold starts. they're backgrounding and foregrounding, which is already fast. the 10% doing cold starts? most of them are patient enough to wait 2 seconds if the app actually works when it loads.

what actually kills startups is frozen screens during app launch. that's different from total time. we fixed our main thread blocking on database initialization (doing sync queries in Application.onCreate, classic mistake) and perceived performance jumped massively even though clock time barely changed.

if you must optimize, measure what users actually experience. use perfetto on android or xcode instruments on ios. cold start profilers lie. look at frame drops and ANRs during load instead.

spend your time on: keeping app responsive, correct data loading, not crashing. boring stuff. shipping features. that's where retention lives.