Implement a 2D convolution (the forward pass) from scratch.
Implementing conv2d proves you understand what a CNN layer actually computes, not just that you can name it. The signal is correct output-shape math, clean stride/padding handling, and knowing the im2col trick frameworks really use.
Updated Aug 2026 · Grounded in real Applied AI Engineer interview loops and written to a senior-engineer editorial bar.
Implementing conv2d proves you understand what a CNN layer actually computes, not just that you can name it. The signal is correct output-shape math, clean stride/padding handling, and knowing the im2col trick frameworks really use.
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.