About your cloud functions / lambdas: do they return HTML content or "pure" data (as JSON for example)?
If your cloud functions return "pure" data, then the client-side JS is doing the rendering: do you manually create the DOM nodes or do you use some templating engine?
If your cloud functions return "pure" data, then the client-side JS is doing the rendering: do you manually create the DOM nodes or do you use some templating engine?