Updating thousands of accounts in near real time is why trading firms have massive computing resources ... racks and racks of hardware, highly optimized software, very high bandwidth servers, routers, etc. Do you think you can get around those constraints ?
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using WebSocket Api provided by the forex broker
Have you talked to your Forex broker, and asked for information about the extent to which they accept/handle the kind of work-load you describe ? Isn't the broker the one who can tell you what you might need on your end ?