While configuration should be read-only, there is a use for read-write state. Currently mongodb is used, which is very convenient as it doesn't require a schema. Only the other hand, the actual data format used in a few places is pretty rigid: tagged and timestamped strings. Furthermore, mongodb requires a separate database server.
It would be nice to not need a separate database server and, given the in-practice rigidity of the schema, perhaps something like sqlite would be good enough.
On the other hand, something with a fixed schema makes it hard for plugins to define their own state types without also maintaining their own databases (not desirable).
While configuration should be read-only, there is a use for read-write state. Currently mongodb is used, which is very convenient as it doesn't require a schema. Only the other hand, the actual data format used in a few places is pretty rigid: tagged and timestamped strings. Furthermore, mongodb requires a separate database server.
It would be nice to not need a separate database server and, given the in-practice rigidity of the schema, perhaps something like sqlite would be good enough.