They used good engineers and a major part of the spec was that speed matters and is the ultimate feature. So when they used the Monaco component the engineers b

They used good engineers and a major part of the spec was that speed matters and is the ultimate feature. So when they used the Monaco component the engineers behind it made sure to prioritize speed and efficiency (it didn't hurt that they could rely on microsofts years of dev tool experience) Technically they didn't do anything insane, the real trick is to measure test and improve metrics they care about and not let it become slow.