Best practices for reducing Android APK startup time and time-to-first-render

[fazi-gondal]

@flet-dev Hi I am working on a Flet Android app named Vidsaver:

https://github.com/fazi-gondal/Vidsaver

It is a video downloader app using:

• Flet
• flet-video
• flet-permission-handler
• yt-dlp
• requests

I have been trying to reduce production APK startup time on Android. The app-level startup has already been optimized so the Home screen is created before storage setup, permissions, downloader code, downloads library, video player, or media scanning are loaded.

Top-level imports in main.py are now intentionally minimal:

import os
import asyncio
import threading

import flet as ft

The first visible page is added immediately:

page.navigation_bar = nav_bar
page.add(ft.SafeArea(content=main_container, expand=True))
page.update()
await asyncio.sleep(0)

Then app services are wired after first render. Heavier modules are imported only when the user actually needs them:

• flet_permission_handler only when storage permission is needed
• downloader.py only when starting a download or scanning existing videos
• library.py only when opening the downloads tab
• player.py / flet-video only when playing a saved video

Even with this, production startup is still slow on Android:

• First open after install: around 13 seconds
• Repeated cold opens: around 10 seconds
• After many open/close cycles: sometimes around 3 seconds

This makes me think most of the delay happens before my app code can render the Home page, possibly during Flutter/Flet/Python runtime initialization, package extraction, plugin registration, or dependency setup.

I would appreciate recommendations from the Flet community and maintainers:

1. What startup time should we expect from production Flet Android APKs?
2. Are there known techniques to reduce Android cold startup time?
3. Do installed but lazily imported dependencies affect startup time?
4. Does flet-video or other plugins add startup cost even if imported lazily from Python?
5. Is there a recommended way to profile Flet Android startup phases?
6. Are there build flags or packaging settings that help reduce startup overhead?
7. Should large dependencies like yt-dlp be handled differently for mobile apps?

Build configuration:

[tool.flet.app]
path = "src"

[tool.flet.android]
split_per_abi = true
target_arch = ["arm64-v8a"]
dependencies = [
    "certifi",
    "charset-normalizer",
    "idna",
    "requests",
    "urllib3",
    "yt-dlp",
]

Release build command:

flet build apk --split-per-abi --arch arm64-v8a --yes --verbose

The main goal is to improve perceived startup and ideally get time-to-first-render closer to 1-3 seconds on modern Android devices.

Any best practices, profiling advice, or packaging recommendations would be appreciated.

[yst-one]

There is also the web version.