Explain backpropagation. Walk through the chain rule for a simple two-layer network.
Backprop is the algorithm that makes deep learning trainable, and the interviewer wants the chain-rule mechanics, not just 'it computes gradients.' The signal is the forward-then-backward flow and why it is efficient. Here is the answer.
Updated Aug 2026 · Grounded in real Applied AI Engineer interview loops and written to a senior-engineer editorial bar.
Backprop is the algorithm that makes deep learning trainable, and the interviewer wants the chain-rule mechanics, not just 'it computes gradients.' The signal is the forward-then-backward flow and why it is efficient. Here is the answer.
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.