Personalize a mobile-keyboard model from on-device typing without raw text ever leaving the phone: federated LoRA with DP-SGD.
Fine-tune a LoRA adapter on the user's typing on the phone's neural engine, add noise locally with DP-SGD, and aggregate only adapter deltas, so no individual's vocabulary is recoverable from the global update.
Updated Sep 2026 · Grounded in real Forward Deployed Engineer interview loops and written to a senior-engineer editorial bar.
Fine-tune a LoRA adapter on the user's typing on the phone's neural engine, add noise locally with DP-SGD, and aggregate only adapter deltas, so no individual's vocabulary is recoverable from the global update.
Lead with where the obvious approach breaks, because that is the judgment they are screening for — most candidates jump straight to the happy path and lose the room.
Then walk the failure back through the pipeline in order, naming the one metric the customer's exec sponsor actually cares about before you propose the fix.
