Oh, I see, now I understand what you are trying to achieve. Yes, you can
indeed modify the TTLs of cache objects in Fastly using edge logic,
overriding the cache control directive from your origin server. To do this
you just need to set
beresp.ttl to a time of your choice.
Rather than making this decision based on a file extension in the URL, it’s
better to do this based on the content-type of the response. I made a
demo to help you try this out: