The Client Blob Cache is a new Bedrock optimization - it allows blocks and biomes to be cached on Clients to avoid resending identical chunks over and over. Chunks and biomes make up the vast majority of network traffic in a lot of common cases (eg. login, teleport or dimension switches) but at the same time, they rarely change. Allowing the Client to reuse chunks it has seen in the past can save a ton of traffic and latency!
The Client Cache is a Content Addressed Storage (a bit like git) that stores Blobs and retrieves them based on their full hashes (BlobIds). This means that the cache doesn't actually know about Chunks - in the future, we might start using it for more types of data, like skins or data driven entities.
A nice thing we get from the CAS approach is that the cache is persistent: returning players will be able to reuse content that was sent them in previous sessions or even previous sessions in different servers as long as tha