Thanks, Author here, yes the observation that it is immutable is correct. One approach you can use is to have some lighter-weight representation for the most

Thanks, Author here, yes the observation that it is immutable is correct. One approach you can use is to have some lighter-weight representation for the most recent data. Then have one or more FSTs representing the older data. As time permits keep merging the new data and the older ones down into new larger FSTs. Merging them is straightforward since you can iterate the contents in order, which is the order you need to build new ones. In this way, it is very similar to having a WAL up front, and one or more segments backing an LSM storage.