Encryption at Rest (Local Device Encryption)

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It's vital to distinguish between cloud encryption (for messages in transit and on Telegram's servers) and local encryption on your Android device.
Telegram encrypts the local database and cached media files stored on your Android phone. This means that if someone gains physical access to your device and extracts the raw files, they cannot easily read your messages or view your media without the decryption key.
This local encryption is typically tied to the Telegram app's passcode lock (if enabled) or other internal mechanisms, adding a layer of protection against unauthorized access to your data on the device.
Cache Management:

Telegram provides excellent controls for managing cached data on Android. Users can go telegram data to Settings > Data and Storage > Storage Usage.
Here, you can set how long media should be kept in your device's cache (e.g., 3 days, 1 week, 1 month, forever). After the set period, media older than that will be cleared from local storage but remains available in Telegram's cloud for re-download.
You can also manually Clear cache for specific chat types or for all media, freeing up significant space on your device.
Data Transmission and Synchronization on Android
When you use Telegram on Android, your device is constantly sending and receiving data to and from Telegram's servers.

Cloud Chats:

Most regular chats (one-on-one, groups, channels) are "Cloud Chats." From your Android device, messages are encrypted using client-server encryption before being sent to Telegram's distributed servers.
The Android app syncs your entire cloud chat history with the servers, allowing you to seamlessly access all your conversations from any other logged-in device (e.g., desktop client, web app) because the data is stored on Telegram's cloud.