Run a lambda every time you GET your object, so it can do data transformations. Seamlessly. You won't even notice until your bill comes.<p>And you won't feel like optimizing this either, because now you have tools and processes that depends on this behavior.<p>Seems easier to me to do this via regular Lambdas instead, but also save the data as an automatic cache for some amount of time. S3 can clean it out automatically. So your lambda will either fetch the cached version or compute it for you upon request.<p>Storage is much cheaper than processing, that's for sure.