In the article it mentions that while indexes are conceptually monolithic, in practice they're partitioned into 3 spaces: historical, current, and in memory.
New data gets written to the log for durability and updates the in memory portion for queries. Periodically indexes are rebuilt, creating new segments for current, and shifting historical data out of current. This limits how much of the log must be replayed on recovery, and allows garbage collection of data that falls out of the retention window.
It's not that dissimilar to solutions used by traditional mvcc databases.
New data gets written to the log for durability and updates the in memory portion for queries. Periodically indexes are rebuilt, creating new segments for current, and shifting historical data out of current. This limits how much of the log must be replayed on recovery, and allows garbage collection of data that falls out of the retention window.
It's not that dissimilar to solutions used by traditional mvcc databases.