features
  finish syncing
    * logging of bytes up/down
    * up/both directions
    * error handling and reporting
    * way to close sync request
    * limit on number of concurrent sync requests
    * full-db scan limited by since/until
  config for compression
  less verbose default logging
  nice new config "units" feature, is 1d instead of 86400
  make it easier for a thread to setup a quadrable object
  opt: PubkeyKind scans could be done index-only

rate limits
  slow-reader detection and back-pressure
  max connections per ip (nginx?)
  max bandwidth up/down (nginx?)
  event writes per second per ip
  max number of concurrent REQs per connection/ip
  ? limit on total number of events from a DBScan, not just per filter

misc
  periodic reaping of disconnected sockets
  ? websocket-level pings