So few people are probably aware of this, but Walmart has this tech internally to power a bunch of things like:

  1. URL shortening
  2. CDN load balancing
  3. Emergency content removal
  4. Emergency content rewriting (removing a dynamically generated cache buster)
  5. A bunch of other things.

We had a few transforms which couldn't be done in a streaming way, like inserting content in the head based on content seen in the body, so we opted to do none of them streaming. Which does hurt TTFB if your content isn't cacheable.