The problem

A family photo app resizes each photo inside the upload request. On a Sunday evening a father uploads 40 photos from a birthday party over a weak phone connection.

Each upload waits while the server makes three sizes. Requests start to hit the 30-second timeout, the app shows "Upload failed", and he uploads the same photos again.

The team wants the upload to end as soon as the bytes are stored, and the resizing to happen somewhere else.