Requirements

Design Overview

Client keeps local Set in sqlite. HistoryEntry has usual metadata + an ID that is incrementing per machine
Client has USER_SECRET
Client gets installed with USER_SECRET
Client asks backend for N, number of registered computers for HMAC(USER_SECRET, "comp_count"). It tells the backend to increment this.
- Periodically it checks the backend for a new N
Sends message to the queue named HMAC(USER_SECRET,i) for 0 --> N asking for history dump
Every time hishtory query is run, it checks HMAC(USER_SECRET,i) for 0 --> N for new history entries
Every time it records a hishtory entry (or batched shortly afterwards) it sends that entry to all queues
With some frequency (once a day?) it reads all queues for new history entries

Once-per-day, it checks if it doesn't have any history entries from other computers within the past EXPIRY days. If it doesn't, it sends a dump request to all queues, then receives their responses