Hi Dima,
the scenario would very likly create an issue at the FE side (Fiori), which has to be tested. In that case I would recommand to establish a "daemon", e.g. asynch. RFC session or APC stateful session in backend system (ABAP engine), which act as consumer of the messages and do the proper aggregation of the data to be sent to the WebSocket clients. Additionaly you should plan a batch job as watch dog to check the availbility/health of the "daemon" session.
Batch jobs, qRFC and bgRFCs as alternatives are - from my point of view - no options, as they do not provide any gurantee regarding the execution time of the tasks.
Cheers,
Masoud