Zstd dictionanaries should be small, max 1MB, and often 128kb to keep zstd fast. If every klient pulled such dictionary once a few months, all event data could be kept and served compressed, very efficiently. This is probably what FB does in it's client? Compression is underrated, we have very fast cpus now, very fast algos like zstd, proper setup will actually increase the client speed and decrease the network data being sent