[NTG-context] ConTeXt's equivalent of standalone class

Coming from LaTeX, when I had some TikZ pictures I wanted to add in my document I would usually keep them on a separate file, I would compile them with the standalone class so that the resulting PDF's size would be limited to exactly the dimensions of the figure. I would then import the compiled PDF in my main document. All this to not slow down compilation times. What's the ConTeXt equivalent of this workflow? How can I keep the PDF dimensions limited to the figure?