i'm not sure if it is worth doing but I had an idea in my head for the simplest version of a binary encoding I could think of and wanted to put it out there.
the encoding-lowercase-hex-tags-as-bytes makes a big difference in contact lists (74kb -> 36kb). its the difference between 1mb and 500kb upload when subscribing to 10 relays with your follow list, assuming something like this was ever adopted.
Well, for the wire, I don't really care that much because almost every relay compresses the data anyway. So, the gain is minimum for all the conversion required.
But for the local db, I thought the biggest gains came from creating a "table" just for all the possible strings in tags + pubkeys + ids + addresses. Then, instead of having 32 or 64 bytes for each tag, we have 4 bytes for an Int, which would be more than enough to represent everything in a single-user db.
However, converting them back and forth for queries and so on becomes quite expensive.
But the savings are really 10-20x.
So, I tried some hashcode methods to avoid having to save a table and convert. That works, but collisions are way higher.
