I'm in Taiwan and we literally don't have any cases of covid. We never had lockdowns, only stay at home suggestions for a few weeks.

Stay at home suggestions for a little bit to get the cases to drop + wear masks to prevent spread + actual contact tracing. See how China does it, that's how Taiwan does it. You scan a QR code when you enter a store so they know where you were and if a case shows up tracing back to the store they'll be able to message everyone that was at it or nearby to get themselves checked.
There's a video on youtube that a Japanese filmmaker who has employees in China made and he covers what he saw the local gov did to contain covid. And no, welding doors shut is literally not a thing.