Intermittently: Couchbase Save Not Happening - couchbase

Question

I am using Couchbase java sdk client 2.7.11 with Couchbase 6.0 community addition. While performing upsert it gives me success response, but when I fetch the document or see through Couchbase UI, it’s not available.
//getClient returning me "api com.couchbase.client.java.Bucket" instance
private static final RetryWhenFunction RETRY_POLICY =
RetryBuilder.anyOf( TimeoutException.class,
TemporaryFailureException.class,
RequestCancelledException.class,
BackpressureException.class,
CASMismatchException.class)
.delay(Delay.exponential(TimeUnit.MILLISECONDS, 50))
.max(3)
.build();
int expiryTime = Instant.now().getEpochSecond() + (10 * 60);
StringDocument document = StringDocument.create("ABC_Test",expiryTime , "SomeValue");
StringDocument savedDocument = getClient().async().upsert(document).retryWhen(RETRY_POLICY)
.doOnError(exception -> {
String msg = "Unable to update a document = " + exception.getMessage();
LOGGER.error(()->msg);
})
.doOnCompleted(() -> LOGGER.debug(()-> "Succesfully saved document with key \"" + key))
.doAfterTerminate(() -> LOGGER.debug(()-> "Processing save document with key \"" + key + "\" Completed."))
.toBlocking()
.singleOrDefault(null);
if(savedDocument==null) {
LOGGER.error(()-> "Document with id couldn't be saved: " + key);
} else {
LOGGER.debug(()-> "Saved document: \n" + savedDocument);
}
I faced the similar issue when trying to use QueuePush. The Queue push gave me the success response but Queue pop says queue itself doesn’t exist. I intend to use both of the saving within next 5 sec for say. I do not have any load test running that could indicate towards Async delay behavior.
//expirationTime is quiet ahead in future.
getClient().async()
.queuePush(queueName, queueElement, MutationOptionBuilder.builder().createDocument(true).expiry(expirationTime))
.retryWhen(RETRY_POLICY)
.doOnError(exception -> LOGGER.error(() -> “Unable to add element '”+ queueElement +"’ in queue ‘" + queueName +
"’ Exception = " + exception.getMessage()))
.doOnCompleted(() -> LOGGER.debug(()-> "Succesfully saved document in queue “” + queueName))
.doAfterTerminate(latch::countDown).subscribe();
Both of above scenario have been noticed intermittently. Could you please suggest to diagnose this one? Does Community Version has a way to enable Document Level Auditing?
I have posted the similar question on Couchbase forum too, trying to bring it for bigger audience https://forums.couchbase.com/t/intermittently-couchbase-save-not-happening/28006 and get the right direction.
Thank you in advance.
Regards