What is this lightning-fast tiny spider?

Many web-dwelling spiders are lightning-quick in their own web (even if they are slow/clumsy walkers outside of their web) so that doesn't help in identification.

Hard to tell from the photo, but it appears to be Cyclosa ginnaga

A better image of the specimen would help identify.

edit after comment:

Here is a gallery of observations (currently 50 of them) of cyclosa ginnaga: https://inaturalist.ca/observations?place_id=any&subview=grid&taxon_id=360502 All those observations were made in South-East Asia or Australia.

You could also look at Cyclosa Insulana with similar range: https://inaturalist.ca/taxa/560706-Cyclosa-insulana/browse_photos?quality_grade=any

But I think the length of abdomen in your photo more closely resembles C.ginnaga, and also the observations of C.ginnaga more consistently show a spiral in the thick webbing while C.insulana tends to be more random.

And here is a breakdown of the cyclosa genus broken down into specific species if you want to browse other possibilities: https://inaturalist.ca/taxa/127360-Cyclosa/browse_photos?quality_grade=any&grouping=taxon_id