Well-written, props. Some architecture questions you might want to think about:

- Why only one elasticsearch shard (+replica) per index? You run some major risks of write-time hotspotting here, especially if you ever have to completely rebuild your indices from scratch (pro tip: plan for it now). If you have any basic metric of a discord server's size prior to index creation, you can pre-optimize the number of shards in its index to ensure that writes are distributed across the cluster.

- What happens when one server's index grows too large to fit on one (elasticsearch) shard? Practical shard size limit in ES is ~50GB due to concerns related to reallocation and recovery. You could also theoretically hit the 32GB memory limit.

Also, as another poster mentioned, consider dedicated master nodes. You're going to lose data nodes from time to time, don't let it cost you consistency by bringing down a master with it.