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/test/java/org/elasticsearch/compute/operator/exchange/ExchangeServiceTests.java
/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the Elastic License
 * 2.0; you may not use this file except in compliance with the Elastic License
 * 2.0.
 */
package org.elasticsearch.compute.operator.exchange;
import org.elasticsearch.ExceptionsHelper;
import org.elasticsearch.TransportVersion;
import org.elasticsearch.action.ActionListener;
import org.elasticsearch.action.support.ListenableActionFuture;
import org.elasticsearch.action.support.PlainActionFuture;
import org.elasticsearch.cluster.ClusterModule;
import org.elasticsearch.cluster.node.VersionInformation;
import org.elasticsearch.common.io.stream.NamedWriteableRegistry;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.common.util.concurrent.ConcurrentCollections;
import org.elasticsearch.common.util.concurrent.EsExecutors;
import org.elasticsearch.compute.data.Block;
import org.elasticsearch.compute.data.ConstantIntVector;
import org.elasticsearch.compute.data.IntBlock;
import org.elasticsearch.compute.data.Page;
import org.elasticsearch.compute.operator.Driver;
import org.elasticsearch.compute.operator.DriverContext;
import org.elasticsearch.compute.operator.DriverRunner;
import org.elasticsearch.compute.operator.SinkOperator;