@Override
    public CompletableFuture<Long> getLatestSequence(final byte[] seqKey) {
        final CompletableFuture<Long> cf = new CompletableFuture<>();
        getSequence(seqKey, 0).whenComplete((sequence, throwable) -> {
            if (throwable == null) {
                cf.complete(sequence.getStartValue());
            } else {
                cf.completeExceptionally(throwable);
            }
        });
        return cf;
    }
Returns a heap-allocated iterator over the contents of the
database.
<p>
Caller should close the iterator when it is no longer needed.
The returned iterator should be closed before this db is closed.
<p>
<pre>
    KVIterator it = unsafeLocalIterator();
    try {
        // do something
    } finally {
        it.close();
    }
<pre/>
jraft-rheakv/rheakv-core/src/main/java/com/alipay/sofa/jraft/rhea/client/DefaultRheaKVStore.java