Write queue size in elasticsearch 6.8.5

settings : thread_pool.write.queue_size: 500 , default value is 200
exception thrown : failed to execute pipeline for a bulk request org.elasticsearch.common.util.concurrent.EsRejectedExecutionException: rejected execution...queue capacity = 500, org.elasticsearch.common.util.concurrent.EsThreadPoolExecutor@766bbb6a[Running, pool size = 32, active threads = 32, queued tasks = 576, completed tasks = 3994308]

i want to know if increasing the queue size to 1000 or more can have undesirable effect on perfermance

It sure can, check out Any idea what these errors mean version 2.4.2 - #5 by jasontedor, which is still relevant today.