A question that has been on my mind for a long time:

How to best deal with lots of data? And is there a way to get rid of obsolete data?

Holochain uses monotonic DHTs, meaning you can only add to it, never remove data. Take a social network as an example, where users tend to upload images. Now imagine I upload a picture of Einstein with a nice quote (all as one jpg). Then I notice a typo, correct it, upload the new file and mark the old one as deleted (remember, the file is only marked as deleted, but its still being stored in the DHT). Then I discover another typo and repeat the process. That way we quickly end up with lots of outdated data clogging up our DHT.

So, how to deal with that issue? Is it best to only store links of files on the DHT and host the files themselves via IPFS? If so, how can we make sure those files are being hosted reliably and with adequate redundancy?

Could there be a purely Holochain solution that allows for the true deletion of unwanted / outdated content? Like, have two DHTs: One monotonic for all the meta-data (publishing / editing / deleting entries) and one non-monotonic DHT for the actual content. Then specify in the hApp DNA, that items can be removed from the data-DHT ONLY IF a corresponding delete-request has been posted to the meta-data DHT.

That way, we would make sure that all relevant data is accessible, while unwanted data can savely be forgotten.