Sending a 100MB video over a patchy mobile connection is a hard problem. Our answer: split every upload into chunks, checksum each one, and resume exactly where the network dropped.
Duplicate files are detected by content hash, so forwarding an album to five groups uploads nothing new. Downloads are verified end-to-end before a file ever renders in your chat.
This deep-dive covers the pipeline design, the retry watchdog, and what we learned shipping it to production.
