Create a 20-second whiteboard explainer on a clean white board. The italic handwritten-style title "How a cache makes apps fast" writes itself letter by letter and a blue marker underline sweeps under it. Then three stations draw themselves in black marker: an outlined arrow labeled "Ask — The app asks for data", a box with a blue tick labeled "Check — The cache answers if it already knows", and a light bulb with blue rays labeled "Remember — Otherwise fetch once, keep a copy", connected by curved gray arrows. Finally "Fast = not asking twice." writes in blue at the bottom and a blue marker loop circles it.