@Override
    public long getLastLogIndex() {
        this.readLock.lock();
        Cursor cursor = null;
        try {
            checkState();
            cursor = this.defaultTable.openCursor(null, new CursorConfig());
            DatabaseEntry key = new DatabaseEntry();
            DatabaseEntry data = new DatabaseEntry();
            OperationStatus operationStatus = cursor.getLast(key, data, LockMode.DEFAULT);
            if (OperationStatus.SUCCESS.equals(operationStatus)) {
                return Bits.getLong(key.getData(), 0);
            }
        } finally {
            this.readLock.unlock();
            if (cursor != null) {
                cursor.close();
            }
        }
        return 0L;
    }
First log index and last log index key in configuration column family.
jraft-extension/bdb-log-storage-impl/src/main/java/com/alipay/sofa/jraft/storage/impl/BDBLogStorage.java