@Override
    public String getLastRevision(String siddhiAppIdentifier) {
        List<String> revisionList = revisionMap.get(siddhiAppIdentifier);
        if (revisionList == null) {
            return null;
        }
        if (revisionList.size() > 0) {
            return revisionList.get(revisionList.size() - 1);
        }
        return null;
    }
Implementation of {@link PersistenceStore} which will store the state in-memory.
modules/siddhi-core/src/main/java/io/siddhi/core/util/persistence/InMemoryPersistenceStore.java