Performing any long running task or CPU intensive work on transport_worker threads is problematic. This is typically very bad for cluster stability.

This issue has been filed to examine the usage of transport_worked threads by ESQL, with the intention of "offloading" as much as possible, including deserialising large(ish) amounts of data.
x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/operator/exchange/ExchangeService.java
private final String sessionId;
        private final int exchangeBuffer;
        OpenExchangeRequest(String sessionId, int exchangeBuffer) {
            this.sessionId = sessionId;
            this.exchangeBuffer = exchangeBuffer;
        }
        OpenExchangeRequest(StreamInput in) throws IOException {
            super(in);
            this.sessionId = in.readString();
            this.exchangeBuffer = in.readVInt();
        }
        @Override
        public void writeTo(StreamOutput out) throws IOException {
            super.writeTo(out);
            out.writeString(sessionId);
            out.writeVInt(exchangeBuffer);
        }
    }
    private class OpenExchangeRequestHandler implements TransportRequestHandler<OpenExchangeRequest> {