Conceptually, Boki provides a log for serverless functions to track state with minimal latency
A LogBook is a virtual log associated with a workflow. We say virtual because it is physically stored along with other LogBooks within a shared log. The metalog is used to access LogBooks within the physical log.
The physical logs are replicated across record stores, which periodically report their progress to the sequencers, who update the metalog up to the most recent fully replicated sequence number
One trick they use to allow for idempotent updates to external databases is by including monotonically increasing sequence numbers in each database entry. These updates only run if the new sequence number is greater.
This log is very useful and the authors provide extensions to allow for common functionality