@Override
    public boolean truncateSuffix(long lastIndexKept) {
        this.readLock.lock();
        try {
            checkState();
            final long lastLogIndex = getLastLogIndex();
            for (long index = lastIndexKept + 1; index <= lastLogIndex; index++) {
                DatabaseEntry key = getKeyDatabaseEntry(index);
                this.confTable.delete(null, key);
                this.defaultTable.delete(null, key);
            }
            return true;
        } catch (DatabaseException e) {
            LOG.error("Fail to truncateSuffix {}.", lastIndexKept, e);
        } finally {
            this.readLock.unlock();
        }
        return false;
    }
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