If not experienced during load shedding, 503 Service Unavailable errors can happen when we are deploying/restarting our fleet of API servers, most users get a graceful disconnect but sometimes you will get a 503.
In this scenario, you should just retry immediately (and be routed to a different host).
If you received this error during system overload, please be aware that orders submitted via the place order panel are affected by load shedding (error 503), while orders submitted using the close buttons on the position table are not.
You can read our System Overload policy here: