After 12:00 UTC on Tuesday, October 3, BitMEX will begin rate-limiting incoming WebSocket connections (as in, opening the socket itself) at a burst rate of 20 connections per hour.
We do not expect this to affect normal users, as our recent (July 8) migration to a Token Bucket rate limiter effectively doubled available capacity for all users.
Additionally, the ability to authenticate to the WebSocket using email and password has been removed due to abuse, and the command cancelAllAfter, when invoked via websocket, is now properly ratelimited.