Technical Manager at AKQA
Nunjucks supports Async operations such as additional conditional content fetches during rendering - when Server-side rendering - this is VERY POWERFUL especially when used in conjunction with a Headless CMS such as Contentful.
e.g. Allow authors to configure List modules with queries and options... when the template rendering runs and we render the module - we can then cal off to get the content to list. Rather than have to have explicit linked references. Get X latest Type, or more complex queries. In React, we would need to resolve and collect all Content before the Render process.